What are your goals for an internship? What are you trying to gain? Just pocket cash? General experience? A trial run with a company you'd consider going full time for? What are your college plans?
Well I'd mainly like experience in something new and something I can put on my CV/Resume.
I also would like to gain some money although I don't expect much and I'm happy with minimum wage.
I legally can't full-time yet as you are required to be in some form of education until you are 18.
After my A-Levels I'm planning to go to Cambridge for Computer Science as I like their course and, well it's quite prestigious but that's well in the future so it can change
The thing to realize is that interns cost companies far, far more in time spent in mentorship than they add in value, even ignoring compensation. The reason to invest in an intern is to help a promising engineer mature, while simultaneously increasing the chance that they choose to go to your company full-time, reducing the (also large) cost and risk of hiring. Trying to find an internship when you're not going to be on the market for 6+ years kind of upsets this value proposition. I'd suggest that if the goal is some pocket money and coding experience, talk to local (non-tech) businesses, figure out what technical problems they have, and offer to fix one of them. Think point-of-sale system integration, etc.
When you say you're happy with minimum wage, are you talking about the £7.55 UK minimum wage for people under 18?
If so, have you considered using some of your time for tutoring other students? Many people pay for online tutoring, both one-on-one and in groups. Check out outschool.com for inspiration.
It may not be the ideal experience you want, but it might be a good way to maximize your per-hour earnings, whilst leaving sufficient free time to work on personal projects, study other programming languages etc.