Well done on getting through the early rounds mate, recruitment interview processes are thorough to say the least! In terms of your interview, as you may already know many people in recruitment (rightly or wrongly) think of it as a sales role... So think of it as your own business... What is your product - high quality candidates, how are you going to source them? Then think about who your potential clients will be, how are you going to identify them?
The first few months should be about building your candidate pool and becoming established with potential clients, you may inherit some existing clients - meet with them and build relationships with them. Research potential clients before you give them a call. Being able to talk knowledgeably about a company will set you apart. There are a lot of recruiters that will just pick up the phone to a name on a database not knowing the first thing about them or their business, set yourself apart from them.
Recruitment is a demanding industry, many recruiters cut corners for 'quick wins', but people have long memories and relationships with clients can easily be damaged. Don't submit CVs for candidates that you know aren't a match for a role just to hit an internal target and if you're struggling to find candidates keep your clients updated about what you are doing in order to get them relevant candidates. You're the specialist in your area and they will respect your opinion.
I hope that helps and best of luck!