You could consider the Sharkoon Drakonia, currently £26 on Amazon but punches well above its weight. You can get the nicer looking black version still under your £50 budget.
Reviews are very good and it has the DPI switch and LED lighting gimmicks people seem to like (mine are switched off), and a couple of extra buttons.
Scan don't seem to sell them any more, but search Amazon for B00889SAE8