Any ideas anyone can do at home with limited access to tools ?
It depends on your interests.
I personally study courses and read books. I do have a couple of musical instruments and some art supplies on the side as well as some programming projects that I can work on. I also have a few ideas that I have been itching to write novels about (if you want, you can do blogging instead).
I do these things to build myself up to make my later life easier.
In terms of down time, I can sometimes play games, watch Netflix, or interact with others on Instagram and SnapChat. If you have home gym equipment (which you should since £100 gear would more or less cover most weight exercises), I'd work out for 45 minutes every other day.
If you wanted to, you can learn to cook. It's a life skill that everybody admires. Alternatively, you can look into growing your own food and assembling your own computer.