Not diesel but bought a 1.8SE V50 3 months ago with 93,000m on the clock, ex bank car with FSH etc. Immaculate condition inside and out and I paid £5400 for it which I feel is about where you want to be for a vehicle with these miles on.
I also have owned 3 V40s and an old shape S40....three of these vehicle were bought with 90000-100000m on the clock with FSH and all were all really superb cars. The other V40 was low mileage 3 owners from new and I have never had so many problems with a vehicle!....kept it two months and then sold it due to the constant problems/faults!! I believe that this vehicle probably was not looked after or regularly serviced!
I have come to the opinion that regular servicing and repair is extremely important with a volvo and I would now always go for a vehicle which has always been serviced when it should be and I believe the vehicle should then go on for ages. Out of interest the lower mileage vehicle was the one that was the most tatty...the higher mileage cars which had presumably done mainly motorway work were all immaculate!
when I was looking I found
www.motors.co.uk one of the better on line search sites and from memory there were plenty for sale your way on there.
Another option would be to look at ex lease vehicles....if you can find the right vehicle which has been leased to a company director etc you might get a good deal??....Auto Infusion Ltd based in Bristol sale a lot of ex lease vehicles of all makes including V50s...might be worth a look on their website or a phone call to see what they have in stock or what is coming in....I know that depending on how desperate you are to buy they can also 'source' the right vehicle for you...I have bought from them and found them pretty good so might be a different angle to look at it from?
Hope it helps a bit
Higgy