Gaining

One thing I think I need to find is some great high calorie snacks that are easy to consume. I'm good with big meals but I never have enough snacks stocked in and I tend to get hungry before bed each night. Does anyone have any suggestions for what I could stock up on?

anything little debbie or ice cream.

Dunno if you've got them where you are but these private selection brand lemon bars are like 400 calories per bar and they're like handheld size or less and they're p tasty too. A whole pack of those (4 come in a package) and a glass of half and half to wash it down would def do the trick

By the way, Private Selection is a store brand exclusive to Kroger, so that's just to say where one might go to get them. It's decent stuff, so it's in no way lower quality or anything like that.

Alas the OP is in the UK, where I'm fairly sure Kroger doesn't operate, so this is for reference for anyone else reading.

Although I'm sure there's lots of bakeries in the UK that make this sweet stuff, hopefully even at a good price.