You might be able to create your combined Tables with SQL (or in a
Macro), depending on just what you want to accomplish.

However, you might consider using a set of Crosstab Queries to display
your results.  Consider the following example...

Since you didn't post any example data, I made up some.  (Most of the
following datasheet views are folded to fit several fields onto one
line, without losing the headers.)

[Tbl Customer] Table Datasheet View:

  Customer_ID  Month  Customer  Customer   Network
                      Code      Name
  -----------  -----  --------  --------   -------
  -1513544438  3      abc       Rasputin   xyz
  -72006585    2      Ccode     John Doe   xyz

  Product  Reason   Quantity   Sales Value  NSV
  Code
  -------  -------  --------   -----------  -----
  p23      Returns  3          $20.00       $4.00
  Pcode    A Grade  1          $10.00       $3.00

[Tbl Scrap] Table Datasheet View:

  Scrap_ID   Month  Network  Scrap  Rework
  --------   -----  -------  -----  ------
  150260348  3      xyz      33     2

  B Grade    (Deficit)/Surplus
  Quantity
  ---------  -----------------
  3          -20

[Tbl Uplift] Table Datasheet View:

  Uplift_ID    Month  Network  Product  Customer
                               Code     Code
  ---------    -----  -------  -------  --------
  -1275920435  2      xyz      223      24
  1814200003   3      xyz      84       13

  Customer Name  Quantity  Uplift  Gross
                                   to Net
  -------- ----  --------  ------  -----
  Jane Doe       27        3       -4
  Jim Stuart     -3        7       21

To make your Union Query easier to edit, I gave each SELECT part a name.
 This allowed me to edit each in Query Design View, although I actually
didn't change much.

[Q_010CustGradeA] SQL:

  SELECT DISTINCTROW [Tbl Customer].Network,
  Sum([Tbl Customer].Quantity) AS [A Grade Sales Units],
  0 AS [Budget Returns], 0 AS [SumOfGross to Net],
  0 AS Quantity, 0 AS Scrap, 0 AS Rework,
  0 AS [B Grade Quantity],
  Sum([Tbl Customer].NSV) AS [A Grade NSV],
  [Tbl Customer].Month
  FROM [Tbl Customer]
  WHERE ((([Tbl Customer].Reason)="A Grade"
  Or ([Tbl Customer].Reason)="Returns"))
  GROUP BY [Tbl Customer].Network,
  [Tbl Customer].Month;

The results of this first one look like this...

[Q_010CustGradeA] Query Datasheet View:

  Network  A Grade      Budget   SumOfGross
           Sales Units  Returns  to Net
  -------  -----------  -------  ----------
  xyz      1            0        0
  xyz      3            0        0

  Quantity  Scrap  Rework  B Grade   A Grade  Month
                           Quantity  NSV
  --------  -----  ------  -------   -------  -----
  0         0      0       0         $3.00    2
  0         0      0       0         $4.00    3

[Q_020CustReturns] SQL:

  SELECT DISTINCTROW [Tbl Customer].Network,
  0 AS [A Grade Sales Units],
  -Sum([Tbl Customer]![Quantity]) AS [Budget Returns],
  0 AS [SumOfGross to Net], 0 AS Quantity,
  0 AS Scrap, 0 AS Rework, 0 AS [B Grade Quantity],
  0 AS [A Grade NSV], [Tbl Customer].Month
  FROM [Tbl Customer]
  WHERE ((([Tbl Customer].Reason)="Returns"))
  GROUP BY [Tbl Customer].Network,
  [Tbl Customer].Month;

[Q_030Uplift] SQL:

  SELECT DISTINCTROW [Tbl uplift].Network,
  0 AS [A Grade Sales Units], 0 AS [Budget Returns],
  Sum([Tbl uplift].[Gross to Net])
  AS [SumOfGross to Net],
  Sum([Tbl uplift].Quantity) AS Quantity,
  0 AS Scrap, 0 AS Rework, 0 AS [B Grade Quantity],
  0 AS [A Grade NSV], [Tbl uplift].Month
  FROM [Tbl uplift]
  GROUP BY [Tbl uplift].Network, [Tbl uplift].Month;

This next one was kind of puzzling.  Since you call for [Tbl uplift]
without ever using it, the effect (if you hadn't used DISTINCTROW) would
have been to multiply your summed values by the number of records in
[Tbl uplift] -- not especially useful, IMHO.  Unless there's a reason
for it to be there, I suggest taking it out.

[Q_040Scrap] SQL:

  SELECT DISTINCTROW [Tbl Scrap].Network,
  0 AS [A Grade Sales Units], 0 AS [Budget Returns],
  0 AS [SumOfGross to Net], 0 AS Quantity,
  Sum([Tbl Scrap].Scrap) AS Scrap,
  Sum([Tbl Scrap].Rework) AS Rework,
  Sum([Tbl Scrap].[B Grade Quantity])
  AS [B Grade Quantity],
  0 AS [A Grade NSV], [Tbl Scrap].Month
  FROM [Tbl uplift], [Tbl Scrap]
  GROUP BY [Tbl Scrap].Network, [Tbl Scrap].Month;

OK, now that we have these Queries defined, it's easy to collect them
with a Union Query.  (It's actually about the same as yours, just
expressed in a way that I think might be easier to maintain.)

[1  Group Together] SQL:

  SELECT * from [Q_010CustGradeA]
  UNION SELECT * from [Q_020CustReturns]
  UNION SELECT * from [Q_030Uplift]
  UNION SELECT * from [Q_040Scrap];

The results look like this, given my example data:

[1  Group Together] Query Datasheet View:

  Network  A Grade Sales  Budget   SumOfGross
           Units          Returns  to Net
  -------  -------------  -------  ----------
  xyz      0              -3       0
  xyz      0              0        -4
  xyz      0              0        0
  xyz      0              0        21
  xyz      1              0        0
  xyz      3              0        0

  Quantity  Scrap  Rework  B Grade   A Grade  Month
                           Quantity  NSV
  --------  -----  ------  --------  -------  -----
  0         0      0       0         $0.00    3
  27        0      0       0         $0.00    2
  0         33     2       3         $0.00    3
  -3        0      0       0         $0.00    3
  0         0      0       0         $3.00    2
  0         0      0       0         $4.00    3

Now, your Query that sums the results might look like this (but I
changed your SQL to abbreviate the name of the Union Query):

[Q_060Sums] SQL:

  SELECT DISTINCTROW GT.Network, GT.Month,
  Sum(GT.[A Grade Sales Units])
  AS [Sum Of A Grade Sales Units],
  Sum(GT.[Budget Returns])
  AS [Sum Of Budget Returns],
  Sum(GT.[SumOfGross to Net])
  AS [Sum Of SumOfGross to Net],
  Sum(GT.Quantity) AS [Sum Of Quantity],
  Sum(GT.Scrap) AS [Sum Of Scrap],
  Sum(GT.Rework) AS [Sum Of Rework],
  Sum(GT.[B Grade Quantity])
  AS [Sum Of B Grade Quantity],
  Sum(GT.[A Grade NSV]) AS [Sum Of A Grade NSV]
  FROM [1  Group Together] AS GT
  GROUP BY GT.Network, GT.Month
  ORDER BY GT.Network, GT.Month;

Its results look like this:

[Q_060Sums] Query Datasheet View:

  Network  Month  Sum Of A Grade  Sum Of Budget
                  Sales Units     Returns
  -------  -----  --------------  -------------
  xyz      2      1               0
  xyz      3      3               -3

  Sum Of SumOfGross  Sum Of    Sum Of  Sum Of
  to Net             Quantity  Scrap   Rework
  -----------------  --------  ------  ------
  -4                 27        0       0
  21                 -3        33      2

  Sum Of B Grade  Sum Of A
  Quantity        Grade NSV
  --------------  ---------
  0               $3.00
  3               $4.00

Now you can display the totals by month, with each network on a separate
line (I suppose I should have included 2 networks... but you'll see them
if you try running this).  Each of the summed quantities that you
display will need its own Crosstab Query.  This one is for [Sum Of A
Grade NSV], with totals by month for each network.  You could define a
similar one for [Sum Of B Grade Quantity], etc.

What I did with the column headers was to display both the month number
and and abbreviated name, such as "02 Feb" or "11 Nov".  This keeps them
in order, but it's instead possible to specify which months you'd like
to see listed (there're a couple of ways to do that).

[Q_070Xtab A Grade NSV] SQL:

  TRANSFORM Sum(Q6.[Sum Of A Grade NSV])
  AS [SumOfSum Of A Grade NSV]
  SELECT Q6.Network,
  Sum(Q6.[Sum Of A Grade NSV]) AS Totals
  FROM Q_060Sums AS Q6
  GROUP BY Q6.Network
  PIVOT Format$([Month],"00 ")
  & Format$(DateSerial(2000,[Month],1),"mmm");

[Q_070Xtab A Grade NSV] Query Datasheet View:

  Network  Totals  02 Feb  03 Mar
  -------  ------  ------  ------
  xyz      $7.00   $3.00   $4.00

  -- Vincent Johns <vjohns@alumni.caltech.edu>
  Please feel free to quote anything I say here.