I will add a little here,, Perhaps some enterprising lad with a bit of time on his hands, AND a service to the BSA community might consider doing a layout thread for the preunit twins models, many of us can contribute where we can. The one issue in my mind is that UK and export models differed at times, and sometimes depends on if Nigel or Simon was working on the assy line that day. Whenever researching this, I tried talking to dealers who uncrated and did prep on these bikes back in the day.
Heres what Cliff "The Sandy Bandit" Mahjors told me one day when I had a Bacon and several other books and was asking about paint layout, graphics, and pinstriping for a model I was researching and restoring. I had found conflicting sales literature, books, period photos and spread them all out on the counter. He laughed and pointed at a plain fender when others of the same year & model had a 1 inch stripe. He said
" Some had this line, some didnt, some were so bad we sent them out for repaint, some were missing the fender all together and it was wrapped in paper and stuffed in the crate and the dealer had to paint it & install it" While curmudgeonly, He was great about giving me or loaning me NOS parts to take back and copy, match paint, or use how I needed. Later when all his stock got bought out and sold in a big warehouse it was all laid out in rows and on shelves. He had bought out Tricor, JOMO, NVT and the other variations and had all the US distributors stock, Was fun photographing it. It was interesting that some of the NOS parts differed from what the books tell us.
Anyrate, My advice on those decals or stickers is dont use them. I bought some too, and while i would NOT leave the seller negative feedback (Kind of a dick move) they are not suitable for anything other than decorations on your toolbox or filing cabinet in your office. The material is wrong, they look wrong when applied, and just are not good for putting on a bike as I believe they will fade, or lift. Trev is right about the other sources, Here in the US though, we have some dealers and wholesalers and they also supply transfers.
Many purists stick such transfers on and leave exposed (They dont last) and in some cases they varnish over the top of them which on many was the factory way depending on year and model. (If you are going to paint over them with modern base coat/clear coats I can write a tutorial on how to properly do so)
Until there is a reference standard on each make & model, what most people do is start with the Bacon books (many errors in there, but still useful) and period photos, others machines that are known history and preferably unrestored are more useful, and then a wide cross section of how the other owners did theirs.
Strive to not replicate mistakes. David Gaylins Triumph restorations book is the best resource out there for 650 triumphs and he is off the charts OCD for research and presenting CORRECT material, But even he does not know it all. (Nice guy though and very helpful answering my questions). But until there is a reference material for BSAs up to the same standards, its challenging to get right. But once you do the research, Its annoying to go to an event and see blatantly wrong applications, And believe me, people WILL point it out.
Oil tank decals seem to be the most improperly applied and bugs the heck out of me. That Made in England cursive script? Yes, commonly used on Nortons, but I have seen a LOT of BSA A65s with them including Original zero mile bikes, Typically on timing side on the frame tubes up near the steering neck. Kenny Dreer of vintage rebuilders & Norton America for a long time used to apply his own version that was added on of "Rebuilt in Oregon USA" or something like that.