Recently bought gel and tray from the smile place (www.the-smile-place.com) - basically you pay £99 and they send you some moulding stuff which you bite into and send back to them to make up a proper tray for your teeth (as would a dentist) -they then send you the finished tray plus gel and you wear overnight or 3 hours daily for a week or so. Very good results and white teeth. A bit pricey but considering the price of some of the toothpastes which are not always brilliant a real bargain. Also the same quality as a dentist which would cost about £500.