If you have the time and the know how then do it yourself. However a buddy of mine recently remortgaged and used a broker - can't remember name.
Basically with one phone call the broker took details, posted out a pack which my buddy responded to by posted all that was required on it, the broker then submitted it to the lender who would take them on at the best one yr fixed rate which is what they asked for at the start. Before the deal closed the received a form that the broker asked them to sign which outlined why he chose the lender he did, i.e. he had to justify the bank he chose to send their case to.