I am 21 years old and currently am working on a OU History degree.
I would be interested in gaining extra income from a franchise run from my home PC but only have £100 to spend. I am not looking to make huge earnings at the moment, just a bit of extra 'pocket money'.
Any suggestions?

I'm afraid that you are not going to find a franchise for that price and most "opportunities" for home working around that price are either for slave labour or simply do not work.
I'll look into this a bit more for you though and post anything I can find.
Kind regards,
Matthew Anderson
The Franchise Shop