I'm afraid I can't help you with a mechanic near Bristol as I'm in Cornwall at this present time.
I think it'll mean asking people for recommendations, scouring local papers etc.
As regards the car. Great stuff on finding an 850 that's had just two owners and has a full service history.
If its been stood for a year then it really needs to have at a minimum an engine oil and filter change. In other-words a service, all fluids checked, brakes checked etc.
One thing I would check on though is when the cambelt/tensioners and water-pump were last changed. This is critical on these cars. A broken belt and your engine is wrecked. Take a read of my 2009 post below..
https://www.volvoforums.org.uk/showthread.php?t=85720
Hopefully if your car has a full service history this won't be too hard to find out, and hopefully the cam-belt job will have been done not that long ago.
All the best to you and your 850. Stick with this forum, there's lots of very knowledgeable people here..
Dave..
