The main qualification is the QFA (Qualified Financial Advisor), below is the web address and i think you can ring up also and request a brochure. I know a few people doing it and its supposedly not that hard.
technically speaking there are no qualifications required to become a mortgage broker, however if you intend on selling life assurance then the QFA1 is required. Most brokers when advertising for a position would favour applicants who have QFA.