a Broker generally charges a fixed fee, a Financial adviser will get a payment from the company you go with (they are required to tell you how much etc), both will have access to deals not available from the in house estate agents financial person, they usually are limited to associated products of their employer. find a product (financial deal) you like get a 'mortgage in principle', then you don't have to go thru all your finance with every agent you go to... you have proved you are in a position to put in an offer.
you pay stamp on the purchase, but check (your solicitor will do this) for any deals for 1st time buyers. We have bought and sold about 10 properties in the last 30 years.