I just recently started looking for a job - I just wanted to ask a question regarding job agencies/consultants here in the UK ? Do they work as headhunters for their clients - meaning their client will just pay them a one-off amount for a staff or do they actually act as 'employers' and bodyshop the IT people to their clients ?
Reason I'm asking is that I want to know how to negotiate with them when the time comes

... I used to work in Singapore and most of the job agencies there also act as the employer (the client companies pay the agencies and the agencies then pay the IT staff). So to the job agencies - they would offer as little salary as possible (sometimes to the point of scaring, insulting you just to accept a low pay) since this will increase their 'profit' from what the companies are actually paying them.
On the other hand - I've gone through a headhunter once and it was a good experience since their goal was to actually have me accept the job offer - so they actually negotiated a good salary for me.
Just wanted to know how agencies here are. Thanks.