Hi Dave,
Welcome to the group. The OM-3 is a wonderful camera and well worth getting fixed up and using. If you can find a place in the UK, that would be your best bet. John at Zuiko.com does great work and he has serviced many of my Oly's. However, he was never fast, and now that he is only doing repair work "part time" his lead times are very long. The OM-2 I sent to him at the beginning of the year took just about six months to get back. This isn't meant as a criticism; we are lucky to have folks like him around. But it is handy to have all the facts.
Also, judging from the cost to ship packages to my niece in England I would estimate that the postage back and forth would be at least half again the cost of the CLA.