Getting Myself to London on a Budget

[BeforeIGoBlinder]

Alright guys, I'm currently in Berlin doing a summer program here. I need to leave some time between the 22nd and the 25th (if i stay in Berlin past the 24th, I need to stay in a hostel). My destination is London to meet up with a friend there.

So far I checked Easyjet and RyanAir. Sunday (the 24th) is insanely expensive (100+ euro!). So I want to fly either Friday (the 22) or Monday (the 25th). I can get a flight on either Friday or Monday from RyanAir for 40 euro before taxes, which is the cheapest fair I've found. RyanAir flies into Stansted and Easyjet flies into Luton. Both of these seems very out of the way, and the cost of getting into London from either airport is about 15 pounds.

Is this the cheapest I'm going to find, or are there cheap flights into Heathrow that I just can't seem to find?

thanks,

Beau