I'd ditch the shreddies for breakfast, most breakfast cereals are just full of crap.
Aim to get protein, good carbs and healthy fats with each meal.
As littlesleeper said above try to get some oats into a protein shake before your workout. As you're in the UK, Google myprotein and get some instant oats from there. It's just oats that have been ground into flour and it's really cheap. Something like £10 for 5Kg. You can just add the to a shake and it makes it nice and thick.
Go to your local butcher and ask them if they do deals on 5Kg of chicken breasts. It's usually about £20-£24 which works out about £1 to £1.40 per breast. Cook them in bulk on a weekend and freeze them in bags of 2 then it's easy the night before just to take them out and have them ready for the next day for hassle free meals.
As for macros etc you don't need to get obsessive about it; for your protein have an amount equivalent to 2 palms of your hand (thickness and size) as much vegetables as you can, have some healthy fats too like olive oil or chopped nuts (a small amount) about 1 tablespoon, or just don't remove all the fat from your meat. For carbs start with about 2 cupped handfuls of starchy carbs in the meal after your workout and the same amount of complex carbs in your other meals. Monitor your progress over say 6-8 weeks and see if you're heading in the direction you want. If you're growing in the right way (i.e. adding lean mass) keep eating like that. If not add an extra cupped handful of carbs to the meals before and after your workout and monitor again and adjust upwards or downwards in the same manner if necessary. Rinse and repeat.
Just read the extra posts re your Dad. Hahaha he's right you know. However I'll give you another tip, if you don't learn how to cook you'll have trouble getting the body you want. Perhaps if you learned to cook your dad would be willing to buy the ingredients you want if it means that he going to get a meal cooked for him too