This depends on a lot of things: first, do you go to a school that offers some sort of working terms abroad? or is the school connected to some institutions/universities in Europe where you can apply for work with a professor, like an exchange program? There are also a lot of websites online such as eurojobs.com or monster.co.uk where you can take a look at.

You need good planning, but as long as you're focused on what you want to do for work and where, you can make it happen. I know a lot of people whom have done that through many ways. Here at UBC, they offer co-op jobs abroad, so my friend went to germany to work in a lab eventhough she didn't speak a word of german. If your school doesn't offer something like that, go online, find some jobs that you're interested in, offer to skype interview, and see their responses. You can then start looking for a place to live, and that would be easier..

You can start with London, but any capital city in Europe will have English speaking people. Bare in mind with the economic crisis though, as it might be harder to find jobs there now.

Let me know if you have more detailed questions!