We've had a recent flood of new people and new questions regarding working in the UK and one very interesting question was whether or not you could visit the UK and look for work.
The short answer to this is: yes. There is nothing in the immigration rules that says you cannot visit the UK and look for work even if you don't have a visa allowing you to work.
However, this brings up a lot of questions and to avoid confusion, I wish to point out:Firstly, we'll just get this out there so that it doesn't have to be said over and over: You cannot work in the UK if you do not have a visa that says you can. If you have any confusion on whether or not your visa allows you to work in the UK you can go to http://www.workingintheuk.gov.uk/ind/en/home/0/preventing_illegal/uk_passport_stamps.html? which has a brief summary to help you out.
Coming into the UK to look for work is very risky. If you were to be stopped by immigration and they found any documentation to show that you're looking for work, they could deny you entry and maybe ruin any chance of moving to the UK at all. There was a recent story of a young girl who was detained and sent back to the states because she wrote in her diary that she had wanted to find work on a previous visit.
If you're looking for work to gain a work visa, it's recommended you find a headhunter who specialises in gaining work for overseas employees in the UK. You have to remember that not just anyone can actually gain a work visa. The IND is very specific in who can get one. All that information can be found on their website. Hiring someone who knows the rules and knows the business would be much more beneficial to you, as a jobseeker, than paying hundreds of dollars to come into the UK and interview for a company who might not even know how to go about getting you the visa.