Thanks crankarm, I know I messed up on this one, funnily enough I read the small print on everything else (insurance, mortgage, etc) - and they all have cooling off periods. I did check out which and how many lenders my advisor checks and where his fee comes from and did a lot of research into rates on money supermarket, etc (including looking at HSBC and talking to my own bank). The quote I've got, although not HSBC, is pretty much what I expected (in fact slightly better) and weighing up the options and incentives I'm quite happy to go with it.
The only one where I missed the vital bit on the back was the solicitors, which turns out to be the most difficult one, so yes, I screwed up and you all have to suffer for it with my panic posts, sorry!

However, the solicitors were not pushed on me, they just suggested it as the whole house buying thing was happening faster than expected and I didn't have one lined up, plus, the fee estimate that I was verbally quoted by the advisor matched the one on the front of the paper, which I was ok about. Therefore, it seemed to make sense just to use them, which now clearly proves to be a big mistake which I might end up paying for - reading the reviews on the web it's not only the cost I'm worried about, but also the quality of service...
But yes, after all the advice on here, I will give them a call first thing in the morning and try my best to get out of it, according to the law society website, there should be something in the document about terminating the contract, but unfortunately this is only a should, not a must and I'm not waiting for an introductory letter from them to see if that gives any details as sending that would probably just be added to the charges!
(And no, the advisor does NOT work for the estate agent, although in my particular case, the estate agent happens to be part of the countrywide group, but that was pure coincidence. And he is on a fixed fee, not commission)