Hi, thanks for the reply.
I'm aiming to achieve Lean Muscle.
		
		
	 
You could probably do this (as a builder with a typical builder's workload) simply by not eating **** and drinking too much.
Make a bucketload of tuna pasta up on a Sunday evening with (per serving)
- Pasta (preferably brown);
- 1x tin of Tuna;
- big handful of tinned sweetcorn;
- big handful of frozen peas;
- big handful of soy beans (if you can find them);;
- big spoonful of mayo (sure it's full of fat, but it's not going to make much difference over a day's work);
If you can't do that in 20 minutes (with only the last 10 minutes actually requiring any effort), then you should really think about your priorities. 
Practically speaking from here, the easiest things (for me) are chicken stirfry with noodles and not much oil and loads of fresh veg.
If you don't have a fridge on site, then you'll have to get slightly cleverer, but that's pretty much it. Big bowl of porridge in the morning, and you'll be set until you get home. 
@ Thorpy: you gained 1lb in two weeks? I lose that much when I go to the loo (mild exaggeration, before anybody starts with the z0mgs!!!111one). If you're concerned about your weight then you'll do something about it, i.e. get a reasonably stable eating routine going - that will do wonders to whatever it is you're trying to get to. Eating erratically does more than screw up your weight, but mucks up the nutrient profile in your blood, screwing with your brain, heart, liver and pancreas. You'll be at a higher risk of heart-disease and stroke, too.
If you're too busy being a student, then be a student for a couple of years, get it out of your system and then start repaying the debt you owe your body.