£800-900 camera kit? What to get?

I'm a 17 year old photographer currently doing A Level Photography. I'm specialising in portrait photography and wedding shots etc. I have around £800, for this I want to buy a camera body, a decent lens, and a cheap ish flash What would you recommend? PS I already have a studio with softboxes etc, I just need the camera equipment as my current DSLR (Nikon D3100) is just not good enough.

You should definitely have a look on Amazon, as it's cheaper than most high street photography shops - but use the shops to your advantage to try the equipment out first!