Just personally bought myself a 08 (Although it is August 08!) V50 D5 SE Lux back in May as a 'stop-gap' car for a year or two before I buy something newer, higher specced and with a T5 engine. I bought it from auction for £6.5k, FVSH provided from a lease company (they all tend to be from lease companies there). It has done 110k and just had its 108k service + cam belt change which isn't a cheap job! Took it to Volvo, and it has a clean bill of health!
I also wanted an R-Design, but actually, having looked at both the Se Lux and R-Design models, they look just as good as each other. So if a Se Lux comes up within budget with a good spec, snap it up IMO.
If your going to get the R-Design, get the SE version. I wanted the R-Design too, but after looking at the specs the non-SE is missing some small little annoying bits and pieces, such as trip computer (This is based on MY2009, which lower milage versions of the V50 are in your budget region).
Personally I'd get the D4 or D5 engines (The D4 (2L) are short-stroke versions of the D5 (2.5L)). Having driven the 2.0D and the D5, the latter pulls a lot better. If you go for something newer with either a D3 or D4 engine, I'd pick the D4. They are exactly the same lump and do exactly the same MPG but they are tuned differently. The D4 has 177BHP (My D5 has 180) and the D3 is 140ish IIRC.
Other things to note: Make sure it has Xenons!!!!!!! The standard lights are poor, whilst improved by using Nightbreakers, they aren't a patch on my dads same-age V70s Xenons.
Whilst it is true the V50 is basically a Ford Focus (P1 platform IIRC), there is a 'Volvo tax' on anything electrical as they are 'coded' differently, even though they are the same part electrically and physically *sigh*. Suspension parts are the same (intact I'm fitting Ford Focus RS polybushes to mine).
Within your budget from a dealer your looking at 3/4 years old with 60+k on the clock.
A black 2009 2.0D R-Design SE with 70k on the clock went at auction for £9k (In-fact I bid on it!) Also, Volvo UK was there with year old cars. A 2011 V50 Se Lux D4 went for £16k! (It was a £28k car)
My overall impressions of the car is very comfortable. The D5 wasn't my ideal engine (wanted a T5 but insurance said no - for now), but I had a budget and I had to stick to it. However, it pulls like a train and returns high-50s/low-60s on long motorway trips at 70 with Cruise Control, so not bad on the old pocket in that department (not that I really care, but it is a back of the mind nag to not see 20 or 30 MPG!).