Well, that is the whole question... is that a serious company? I never heard about them before but found some gear on their site that I would like to buy.
I've never ordered online. Their store is local to me here in Phoenix,AZ. I've purchased a number of lenses, bodies, and sundry items from them over the years. They've always seemed knowledgable and well staffed. They definately have the film era expertise, being "colllectible" oriented and all. They aren't a fly by night if thats what your worried about. I can't speak to return policies etc. I've never had to return anything. If they've got what you want, give them a try.
If you mean the UK based one, http://www.collectablecameras.com/ then yes, I've used them a couple of times, with no problems. Excellent service, in fact. I had one item ordered from them with a minor problem [damaged cable connector on a flash, but not something that'd have been obvious on an inspection] and they sorted it out promptly and with no problems at all.
Collectable Cameras in Yorkshire - very good to deal with. I have bought from them, and their prices are lower as they do not have High Street business premises. Missed a Leica R camera 3 weeks ago. I think it was Mint -, or thereabouts, but it seemed to have been snapped up straightaway. If you get the chance to visit Simon's premises, it is well worth a visit, but take plenty money with you - you will be drooling, and want to buy, buy, buy. !