I've found that mid range Logitech stuff seems to suit me best. I did have a Razer mouse previously, but I felt it just wasn't as good as a Logitech, even ignoring that it cost significantly more. A MX500 corded mouse does me fine, cordless are just problem magents - and is there any gain really? Razer kit just seems to be LED lights and marketing. The keyboard I have is a Logitech Media 600 and it's great. I just toss it every 6 months when the keys get worn smooth. The only keyboard I'd consider instead would be one that worked after a washing machine (my previous 600 was a little flaky) but which also had keys that didn't go smooth.
So in answer to your original question, you should be spending £46.98 on a mouse and keyboard.