I found a heavily discounted gaming (I hate the term, but that's how they market it) mouse pad in Currys some time ago, down from the exorbitant £20 or so down to £7, and it really makes a difference. The one I got is between 1 and 2mm thick, so you don't experience a ridge that would be in the way of your wrist and it really allows the mouse to glide. You get virtually no resistance and it's a consistent surface, much better than the piece of wood making up my desk. No way would it be worth £20+, but for what I paid it's great.