Waxy maize is good, I'm using 2/3 scooops post workout, then 20 minutes later 2 scoops of whey.
Myprotein do 5kg for £17 which'll last you ages
Fishoil from holland and barret can be cheap if you buy when they have a good sale on... aim for 10-15g a day (it sounds like a lot but it will really help).
I personally try and stay away from fat, carbs and protein as suggested in that shake. I'd take out the peanut butter personally. Sounds ok apart from that. I have oats/whey shake with an apple and a couple slices of toast in the morning personally. Works for me!
You could probably afford to spend a little more time in the gym... no need to stress over it too much. Maybe a couple more sets here and there if you feel up for it.
Keep it up!