I already have bookmaker accounts, can i still make money?

Yes. In fact, in some ways having existing accounts is an advantage.

You won't be eligible for 'new account' bonuses but, it is likely that the bookies have profiled you as a regular 'mug' punter.

This is good because it will provide additional camouflage for your matched betting activity, meaning that the bookies are less likely to restrict your accounts.