£1 profit and >250 markets and you potentially qualify so it's never to late to start thinking about it. In fact anyone who isn't thinking about PC mitigation early on it isn't planning on winning long term.
£12, 1000 bets, +£750 net....iro 6¼%
That's a decent start for a backtest, they usually slip about 30% (?) going live so you ought to be left with 4%+ which is the realm of believable.
How did your in sample and out of sample tests compare, similar?