The camera came back with new light seals and a new on/off switch and seems to work fine.
This is a 'self portrait' taken in a mirror from the test film I put through the camera when I got it back. The repair guy suggested that I set the meter 1 stop faster than the film (400ASA for 200ASA film) as he tested the meter and found it was a bit weak.
The question that arises with OM-1 cameras is what battery to use. The original mercury cells are no longer available. I have been using hearing aid batteries (1.4volt 675ZA - you can get theses in Boots the chemist in the UK). However these batteries don't last very long. I though I would try so called Wein cells. These can be purchased in the UK from the Small Battery Company (www.smallbattery.company.org.uk/) but are quite a bit more expensive that the 675 hearing aid batteries (£5.20 ea) but are supposed to last a lot longer.
I'm still not convinced the meter is really accurate so as soon as I have some time I'm going to do a proper series of test shots to calibrate the meter properly