Budget depends on what features you want. Personally I'd look to spend round about £80 and get all the comfort features - towelled straps, padding on the buckles, proper knee padding and hard wearing material at the bottom of each pad so they don't tear so easily.
I use Neon pads and have to say they are excellent. CBF discount code will take a fair whack off the price and they now offer a more budget friendly range too which, with discount, will be just a little over your stated budget. Really comfortable, well made and mine have lasted two seasons with constant use.