Very nice restoration. I stumbled across this looking for infomation as I have just been given My Uncles old Langsett frame and forks. It appears to be a 1960 build, and possibly a "competition 55 special" or something to do with the celebration of the 1955 Tour of Britain success. (It has different head and seat tube badges, that state 1st, 1955 Tour of Britain on them)
I am off to Langsett on Saturday to pick up a book.
Did you sort the decals yourself? I may be back pestering you for advice if you did.
Dave
Feel free to ask any questions you want Dave. If I know the answer I'm happy to help.
I've got the Langsett Book myself and the decals did change in 1955 due to the Tour of Britain as you suspected. There are also changes in the paint work from mine. I believe the seat tube 3 colour banding is replaced by a one colour band. I think the 1955 bikes had chromed shoulders on the forks too. There is a nice photo of the 1955 bike in the book so it should be easy to replicate the look. Also if you have the frame number then the book will also tell you the bikes original colour.
The decals on mine were created from scans from the book I then re-coloured and sharpened them using Paint Shop Pro. They were put on the bike using Inkjet Water transfer paper and then lacquer was applied over the top. Took a long time but they're well worth it for the overall effect.
Let me know how you get on with your project and, as I say, if you need some help/advice just send me a message and if I can help i will.