Why bother? hate to sound negative but everyone got the same business idea...
Loads of unemployment... why not set up a recruitment agency?!
A heavily saturated market - there can be advantages on a single location but limits expansion potential - increasing competition by the month (be prepared for rivals that pop up out of nowhere; don't expect such start ups to be in yellow pages and have a website already) - but the main underlining concern simply is (although companies are employing...) businesses are not employing no where near as much as the huge unemployment figures.
What I would say is do extensive market research - do not overlook SWOT analysis - its not so much about small USP and your offering but this market is ALL about your competitors.
You need to be prepared for loyal employers sticking to existing agencies, employers doing it alone (non-agency work), influence of banks (at least one big bank I know of offers extremely competitive payroll services for first year) AND agreements agencies have with employers, that you wont know about until staff are taken on through the agency or until the position is vaguely advertised.
Its hard work as agencies litter job boards with jobs they don't actually have - it can be for the wrong reasons (increase dominance, get jobseekers signed up etc.) or the not so wrong (but still wrong) reasons (promoting a vacancy to get an employer on board, before there has been any agreement). If you noticed, I am using the term "employer" loosely.
I know many small agencies and they only have 3-15 new leads each month, and a handful of clients (lets not use the term employers), with a small pool of agency staff recruited. It can still work and be profitable but when factoring a fulltime week, you need someone manning the phones in office hours and you need to be constantly networking and building on relationships with potential clients.
It really is like launching a ship for the first time, hoping it doesn't sink or roll over, and more so hoping it doesn't leak in water.
It will take a while to make money - but many on this site has considered how they will operate their start-up recruitment business from home or get a cheap office in the middle of nowhere... to lower costs and provided an affordable service. It really does pay for a good location - if you aren't in the town centre (at least!) its a disaster from the beginning. There is nothing stopping you having a small shop, and operating out of an office elsewhere.