Hi,
I'd strongly recommend a Rover as they're significantly less expensive to buy than many other cars of a similar age though are often more highly specified and better finished.
The Rover 200, or subsequently 25 is excellent for short journey's and the 1.4 petrol and 2.0 turbo diesel both offer good performance and good fuel economy and emmissions. For �2k I'd imagine you could get a high spec low mileage 2001 - 2002 model.
The 400, and subsequently 45, offers a great level of refinement if you can forgive the dated interior. The exterior, especially of the saloon, is very stylish and modern looking. Make sure you choose a model with Air Conditioning as it will hold value a bit better, and add comfort in the summer. �2,000 could get you as recent as 2003, or maybe even younger if it's high mileage.
The 600 isn't quite as economical but the turbo diesel offers a reasonable mix of economy and performance, though not as refined as Mondeo's and Vectra's it is far more individual, looks great, is much cheaper to buy and is far more reliable (Honda mechanicals). �2,000 will buy you an absolutely top specification 2000 model with low miles. The ride quality, power, handling and interior comfort far exceeds that of the BMW 3 series.
The 800, though an excellent car, probably isn't suited to your requirements.
Alteratively of course, there's always a Vauxhall Corsa 1 litre... which will do the job but isn't a patch on the Rover 25, though will in all probability hold it's value a bit better.
You could always consider a brand new Kia Picanto which though well over your budget is only �5,000 and they often have 0% finance offers, and you get the benefit of a 3 year warranty.
Hope I've been of help!