Buster is right. Luton is very welcoming to light aircraft . . . it does just happen to be quite expensive (although still cheaper than Stanstead I believe). I regulally fly out of there in a club PA28 and find that almost without exception, the guys in the tower do their damndest to minimise delays and fit in my landings/take off's between the big guys and for that, I thank you (even when it occasionally doesnt work out and we have to break off an approach).
If you want a cheap field with good facilities, try Cambridge.