Ralph, head over to scalemates.com and type in the kit you have. For the current GB we'll use Bill's Tamiya 1:48 Spitfire Mk.V as your kit. The site is peculiar in that they want 1:48 and not 1/48.
Enter it into the search bar and select the top choice
The kit....
Decal choices...
There is a timeline that shows the history of the kit which is clickable and also most have a PDF of the instructions
As you know, most instruction sheets show dates and locations for the decal options so its just a matter of going through the instruction PDFs and looking for the appropriate option