Currently selling our house and going to be buying as well. Our current mortgage provider has told us what we can borrow and what rates are but I have looked on money supermarket and have seen better interest rates although I can't guarantee they would accept us, although I don't think it would be a problem. I spoke to or adviser on the phone and he said stay with our current provider (nationwide) as they aren't the worse ones out there.
Would you shop around yourself (and if so where?), stick with your current provider or go to a broker? What have you done in the past?