If they've settled a winning bet and it's showing in your balance and you then withdraw the funds to your bank account, can they retrieve it again if they realise they've made a mistake?
Most of them do " best odds guaranteed" could it be that? I placed a bet at
20-1 once and it paid out at 33-1 which was the eventual starting price.
But to answer your question, no they cannot take money from your bank account and its very unlikely the computers would make a mistake. As Psybs says, let us have the odds and we'll see what we make it.
I closed my WH online account on monday. They sent me an e-mail telling me that due to the fact I hadn't used my online account for 24 consecutive months they were going to debit my bank account £3 every month !!