I have no idea what to cook!

try this website

It has guidelines on healthy eating & balanced diets, as well as meal suggestions.
For more help try typing "healthy eating balance diet" into google

Generally speaking, your diet should consist of carbohydrates (pasta, rice, potatoes) protein (meat, fish, cheese) & fat. In addition you should be aiming to eat 5 portions of fruit & vegetables per day & choose unsaturated fat.

This is long cos I'm writing down what springs to mind:

Eat breakfast! Always.

Consider taking coffee with you in a flask unless your union shops are really cheap. It may look a little geeky, but less embarassing than spending £1 on something cheap and nasty.

Don't buy ready made tomato or chilli sauces for pasta and rice. Put aside an hour or two in the kitchen each week to make an enourmous pot of one or other such thing, cool it down and freeze in you-size portions. This way you'll always have something ready but if you feel like cooking it'll keep.

Beans and soya are cheap and tasty sources of protein, esp if you buy the beans dry and soak and boil.

The library is likely to have some good books on "student" cooking. My favourite was Silvana Franco's vegetarian student cookbook (my favourite recipe from that below). There are a couple of new ones out recently: I think Beyond Baked Beans and Cheap as Chips, Better than Toast. Meant to be good.

My favourite recipe from SF is potato pie - more impressive than it sounds. A layer of boiled sliced potato. A layer of tomato (either fresh and sliced, or tinned and drained). A finely sliced (fried if you prefer) onion. Dried herbs. A layer of mozzarella. Another layer of boiled slice potatoes. Another layer of mozzarella. Bake until the top looks tasty. At about 80p for the mozzarella and at most the same again for the rest of the ingredients, it's a scrumptious meal. Serve with veg or salad and it's pretty healthy too.

Crumpets are lovely pizza bases or just for a different cheese on toast - the cheese melts in to the holes and it's scrummy and quick - check Delia online for ideas for other toppings.

If you're sharing a fridge with other people consider going to the pound shop and buying a box which you can lock with a padlock. Although I didn't have many problems with people stealing stuff, you all tend to buy from the same shops so it's hard to tell whose stuff is whose - you don't want to come home desperate for a nice coffee to find someone's nabbed all your milk!

Find a recipe for oat based cookies of some sort 9not flapjack!). So easy and quick to make, dirt cheap, will keep a couple of weeks (mine never last that long though) and you can use them for snacks instead of expensive cereal bars. If you're too late for breakfast they're not a bad substitute with a couple of bits of fruit.

Doing as much cooking of your own as poss might help you keep on track because you'll know exactly what's in everything.

Pizza is also v easy to make yourself - you can use some wholemeal flour in the base to make it more healthy, and add all your favourite veg on top. Nice for sharing with friends which brings me to my last point - consider sharing the chores by cooking one night for friends and letting them do it another night. But be wary of sharing shopping with a group (beyond the obvious bulk buying of rice, pasta, and household stuff). It can be easy to actually wind up buying more because of pressure and the fact that spread out it looks like you're spending less. Share your stuff, but keep to your own budget unless you find someone really trustworthy!