Unfortunately, I think that your smoking- whether tobacco or e-cigs is a luxury you cannot afford. How much of your money would that free up if you could give it up? Can you speak to the hospital about support for quitting? You would probably get access to patches, etc for free- I know local GPs offer these services.
I honestly think that the one thing you need to prioritise from your £100 and your CB is food. Why are you still trying to put money in their child trust funds? Think to yourself, if you got to 18 and got told that you had a bit of money in the bank, but that your mum and you had to rely on a food bank for however many years to give you it, would you honestly want it?
As for parties, ice creams, etc- well that £10 each a month can be used towards that instead, maybe. I honestly think that's a much better use than savings.
Bills- yes to the warm home fund, as someone else has pointed out. You have internet access, so fill in a form on compare the market- are you on the cheapest provider for your utilities? Are you in credit, so you are actually allowed to switch?
In hospital, are you paying for the TVs, etc, there? Those are ridiculously expensive, so if you are, would you be cheaper to sign up to GiffGaff or somewhere with a high internet usage allowance, and watch on your phone or a cheap tablet instead?
Snackwise, you are probably going to have to take cheap snacks with you if you really can't manage on the 3 meals a day hospital provides- although, to be honest, I actually think you need to try for a week. Your stomach is used to feeding at a certain time, and you might find that after a week it shrinks a little and adapts, and those 3 meals are OK. If not, is there a patient kitchen you can use? Take a loaf of bread for toast, or pasta pots from Aldi? If you do really need snacks, then limit them- Make a big pot of pasta for the first couple of days on a Sunday night, and take a multipack of crisps and a pack of cereal bars. But, to be honest, I don't think you can afford to snack, sorry- feel horrible saying that.