Normally takes 3 months to get the money back and you never get as much as you're expecting. If its 10 %, it will be before vat. If you're using a discount code, you may not get any cashback at all...

Like Mac says it is usually 3 months, some retailers pay quicker but some take forever as well. Well worth using though, I use it wherever I can providing I remember! More and more are declining the cash back now though which is annoying but its surprising how much you can build up for stuff your buying anyway. Topcashback is another one, sometimes their rates are better.