Okay, I was in the same situation  a few months back though I do a fair few more miles than you a year (approx 80k). I bought a 54 Honda Accord Diesel from Honda in January with 57k on the clock for £5500. It came with a years warrenty, its costing me £236 a month on 2 year finance. Bargin! I get 550miles to a tank of diesel (£60 to fill) Its cheap to service (£175 - £220) and tyres are dirt cheap (£70 a corner).
I plan to get a newer 56 - 57 plate Accord Jan 2010. Im expecting £1.8-2k on trade in, so the cars cost me £3.5k for the year or just over 4p a mile. I chose the Accord because I wanted reliablity, plus as a Field Engineer and Director of a sub-contracting company I didnt want to rub people up the wrong way and turn up in a BMW, Merc Audi et el, Hondas seem none offence to all.
I'd recommend the Accord for reliability and comfort to anyone, Im sure an Audi or BMW is a better drive, but Im less convienced theyre as economical day to day