Each of the brands have released good beginner models, really there isn't a great deal of difference between them in that price bracket. Best advice is go down to your local camera shop and get a feel of a few camera bodies and decide which you feel comfortable holding, operating the controls etc. Canon and Nikon are the street leaders, canon offering the largest selection of lenses, Sony have come on great guns since they launched their 1st DSLR, then Pentax and Olympus following up in the rear.
Personally don't dismiss the 2nd hand market, you can get quite a few bargains, camera models although a few years old, still better than the beginner models brand new, like the canon 20D for around £200-250, money left over for a reasonable lens.
Personally I'm not a great fan of the nikon D40/40x/60/3000/5000 range of camera's, they're good camera's, however, nikon have pushed you down the road of a new series of lenses with autofocus built into the lens rather than the body (AF-S or AF-I designation in their name) and I think you miss out on a large range of their older quality lenses, especially primes for which the Nikon D70s or D80 would be a better option to go for instead. Just my thought's
