@macarony

"I also dont understand the bit about not paying 20% in charges, thought you pay as you win in my case 5% on every winning bet."

So you bet £100 at evens, you win £100, you pay 5% - £5.
You bet another £50, it loses.

You are now £50 up on betting and have paid £5 in commission - that's 10%.

Etc, etc.  On my best-ever winning strategy I paid just over 50% in commission.