Japanese food!
A lot of it is easy (<10 ingredients, not horrendously time sensitive), quick to cook (usually <30 minutes, not much longer on your first try), fairly cheap (£1.50-£2.00 for a good sized portion), and it's pretty healthy (plenty of veg and it's you can pretty much use whatever kind you want providing you know a little about how to prepare it).
Try Butadon and Katsu Curries to start, the former is short and quick, the latter takes about 1hr if you make the sauce from scratch but you could easily do it in 20-30 mins with a ready made mix, but is pretty delicious and will introduce you to some cooking techniques which are a bit more advanced than your average student's repertoire, but not too difficult e.g. making sauces and shallow/deep frying.
If you can plan ahead then try marinades, there are quite a few recipes out there which will require you to make a quick marinade then chuck stuff in the fridge for maybe an hour, though some recipes will take longer to marinate, but once you get to cooking it will be pretty quick.
You can also kinda wing it. Once you have an idea of what spices and combinations of spices are good, you can make something with some flavour with minimal preparation, then just have some assorted veg, rice, or bread on the side.
As a general note, try and stick to rice based meals. It's cheap as hell (get a 5kg bag for less than a tenner and it will last you all year), it's quick to make at ~20 mins, and it's healthier than alternatives such as chips or bread.
Like claire said, there's always spag bol. It's quick and easy, it's reasonably healthy, you have good control over portion size as you can easily store leftovers and you can do meat or no meat, even the good pre-made sauces are pretty cheap, go for Loyd Grossman when it's on sale or Ragu if they have it. You can make your own fairly simply but honestly you don't save that much money, especially if you use quality ingredients, and it takes a decent amount of time, particularly if you're doing it properly.