If you're in London then I would use Swiss Time Services. They are the approved service centre for Omega & handle loads of vintage watches:
http://www.swisstimeservices.co.uk/ Apparently, they have 15,000 Omega's going through them in a year.
They are in Southend & it is worth going there if you can. They will agree exactly what to do (and not do) with you & tell you how the watch was originally supposed to be. If you can't get there, you can do it all by post & email/phone. Personally, I prefer going there. They did a great job on my 1970's Seamaster Chrono at a very reasonable price.
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