I would say real estate is mostly always a good investment, (especially near tube stations or Universities) but then again im not a homeowner myself yet, Bitcoins, imo i would say yeah invest in Bitcoin too because if it takes off, its going to reaaaally take off, if it doesn't it doesn't but you dont need to invest very large amounts unless your pockets allow for this (never invest more than you can afford to loose as they say)
As for the UK, property could give you decent return in relatively short time. Aim for cheaper houses (< GBP 100k, affordable for first time buyers), preferably repossessed by bank, located within less than 1 hour drive from the town centre of any major city. Don't do any major work on it, just refresh the look, give it a proper cleaning and re-paint.
If you're lucky, you can pocket out 30-50% profit in few months. If you struggle to sell, you can always try to rent it out.
As for Bitcoin. Definitely too risky to invest large % of your wealth in it. But as someone said on this forum: you have to be clinically retarded not to own some, just in case.
When you say less than 100k i dont suppose you mean anywhere in or around London? if you do, if you don't mind pointing me in the right direction =) would be appreciated lol
also, how would one go about buying repo'd properties? auctions?