Have you visited the websites mentioned to see what is outlined?
Some mortgage brokers refund the commission they receive from the mortgage provider to the customer (but they charge a fee for their service?).
Others offer conveyancing packages at discounted rates.
Some may be able to get you more money than by going directly to the mortgage provider.
I'm sure Sarah W will be happy to outline what Rea typically provide. If you use the search facility you should be able to find previous discussion on the topic.