If you want to practice BO before committing any real money, you can open a demo account on "IG.com", without depositing anything. Their "sprint markets" are essentially the simplest implementation of it, but there are a lot of other BO options on there. They are regulated by the FCA in the UK too.
I've spent a good bit of time looking at various brokers (24Winner, AnyOption, Nadex etc.). Most of them feel more like casino web sites rather than a "proper" trading site. The fact that IG have a physical address in the UK listed on their site and are FCA regulated gives me more confidence in them than a lot of others, but I was only attracted to them as they actually let you demo without parting with any cash. It would seem suspicious to me to not be able to do that on a platform before investing.
As has been pointed out before though you need to be hitting a target of at least 70% accuracy with good money management to make any sort of decent return. If you could do that, you could easily turn £100 into over £1,600 doing just one trade a day for a year (risking 3% of your capital each time on an average return of 80% of your stake).
If you can get that up to 80% it rockets up to about £12,000. Good luck with that though.
Likewise, if you "only" hit 60% it's closer to £235.