Advice on buying a new USB graphics tablet?

I have been using my old unnamed tablet for a few years now but its on its last legs. I have been looking on amazon at the various models available but am struggling to make a decision. The Wacom tablets seem to be the most popular but also the most expensive and I wonder how much of the price is just paying for the name. I cant afford to pay more than £50 uk. Does anyone have any advice or reviews on what they use?