well if you want to work hard and do very early up to night flights (read Athens/Malaga) go fly out of LTN. But I'm afraid you don't have a choice in the matter.easyJet will assign you a base and they will try and accomodate your preference as best as they can.
You will now at the interview stage which aircraft type you will be flying, so then your base possibilities will narrow down aswell.
Immediately you can be put on a base transfer list if that base has got your aircraft type that is.
I wouldn't care too much which type to fly. 737's are a good laugh but they say the Bus is far more pilot friendly and a better environment to work in (less noice, ergonomics etc.).
the old -300's are always a challenge especially in the winter!