i dont know of a service that charges for computing power used.
the only ones i've seen are based on what hardware you pick to rent.

what's your budget?

it is just a personal project atm so $100 per month, preferably less

I thought amazon's cloud computing is per data?

what do you need it for?

optimizing genetic algorithms

There are online render farms out there if you're using it for graphics, but in my expereince they were hopelessely overpriced, though you might get more GHz for your buck these days thanks to intel.

The i7 2600k is a bargain and gives you a lot of processing power for your money, for under £500 you can have a power house as you said you don't need a GPU.

You could buy 4 of those and have some admirable power for under 2000 or whatever the budget, you;ll go through a stack of cash using remote options and won't have nothing at the end of it if your needs grow/continue and I'm not convinced you'll have the freedom you want.

For graphics there are lots of expensive options, for other stuff, all the stuff I heard off sounded very beta.

Or convince someone at a university to let you use their super computer.

super computer is a bit of overkill as i need it to run windows/server. I am currently looking at used 4 xeon dell poweredge6600 for ~300 quid as an option.