Gradcracker.com has some good stuff if you're allowed to go international, but a lot of it is for military contractors so you won't be able to get security clearance as a non-UK citizen.

You'll find a lot of stuff on linkedin, which also makes it easy to apply for a lot of stuff. Even as a student you'll probably get some recruiters annoying you from time to time if you fill it up properly.

Your college should have a jobs board with lots of internships (I say should because I remember DIT just had a portal to gradireland, which is shit since it's all """graduate""" jobs in marketing and sales for people with 1-3 years experience).

However when I was looking for a summer internship I found that I got further just by emailing directly asking if the company had any internships.

If you want, I actually made a spreadsheet of several companies that do internships that I intended to apply for this year (until I transfered to a different college where I won't be doing an internship this year).