It might help us to have the following questions answered:
1. WHY are you looking for people? If it's to track down friends or relatives who would probably be happy for you to find them, the task might be fairly straightforward; if it's to track down someone who's trying to avoid repaying you money you've lent them, the task could be considerably harder.
2. WHERE do you think that they might be? It's absolutely pointless if we direct you to a UK site but the people you're looking for are, say, in the USA.
I've assumed that you're actually trying to locate people. If, say, you already know where they live but you want to check whether they've been declared bankrupt or have court orders for the repayment of debt made against them, we'll need to direct you to different sites (and, again, we'll need to know which country they're in).