The easyJet Academy has a kitchen area for students with microwaves and fridges. You can use these in the evening as well as lunchtime.
Asda supermarket is a 10 minute walf from the Academy, and the Luton Flying Club is a 1 minute walk, which serves hot and cold food.
Get friendly with someone who is going to be LTN based on your training course. Most of the LTN crew will live locally and have a car, so you can get taken out for dinner!!