Tied in, or?

[TinTin]

Newbies galore

DG, it's like the blind leading the blind with so many newbies around. I despair sometimes not so much at the lack of professionalism, but just general knowledge stuff that seems to escape them.

[XLMonkey]

Say I pulled out of the contract; what consequences can I expect?

Well, you've signed a contract to provide the services, so if you break the contract, then the other party is entitled to sue you for:
- loss of the services (in theory, they can take someone else on at a higher rate and then make you for the the difference)
- the cost of securing someone else (so, the agency margin that they are paying for taking someone else on).
- any loss or consequential damages that they incur as a result of the time it takes them to find someone else (though on the bright side, they will have to prove the extent of these damages, whereas in for the first two sets of costs they don't have to prove very much at all).

.... or they could just blacklist you from all future opportunities and tell all their mates to do the same...

Generally, you should remember that if it looks like a contract and smells like a contract, then it's a contract (even if it only says "Letter" at the top).