Dar,
I just bought a nice 3yr old VW, and financed it through VW Finance. I have no credit history here either, but I do have the advantage of being a citizen, having a UK driving license, and being able to put down at least 20% (I actually did 40%). I'll do the payments for a year, and hopefully by then my US house will have sold, and I'll be able to pay it off completely. The interest rates here are horrible compared to the US. I did get a letter from my employer, confirming my employment and salary. That helped a lot.
In your situation, I'd be looking for a decent £1k car to get me by for a few years. My parents have a '96 Citroen that they paid £1400 for 5 years ago. My brothers have been sharing it as a car for the last few years, and it definitely isn't pretty, but it starts every time, and costs next to nothing to run. Do a search on Autotrader.co.uk. There are lots of Ford Fiesta's and Peugeot 106/206's out there that will be cheap to buy and run.