Original brakes were probably GB Coureur calipers with GB Superhood levers. That bar is probably not original; it is off a Dawes. You'll find one end engraved "DAWES CERTES ENGLAND" or something like that. It is perhaps the prettiest bar ever made; hang onto it for sure.
Actually, all of the parts can be found; but it doesn't really matter. Once you start buying 1950's bicycle parts it is hard to stop, because first you compromise and then you find something that's closer to original, and every time you bid on ebay you're bidding against some other nutter (i.e. me most likely
).
Congratulations at any rate, it will be a beautiful bike.