Heyyy, I used the Cosmetic dental clinic in Newcastle and I would highly recommend it. My dentist Andy was an absolute star, I had an invisilign brace and whitening along too so the price was subtotaled all together. But they have some great offers on and I know that for the whitening the cost goes towards the trays and then after that its £20 per whitening tube for when you want to top up.
I have had my trays for a year now and need to top up approx every 4 month. not even that. so although the trays are expensive at first. It is definetly worthwhile in the long run Definitely recommend it x
http://www.thecosmeticdentalclinic.com/