Fast Funds is the quickest way to make a withdrawal, and get your funds from your Betfair wallet to your bank account. Fast Funds is currently available to customers in the UK, Ireland and Spain with a Visa Debit or Prepaid card.
For this reason alone, Betfair has no reason to ban or close your account when you should win. This is what Betfair first became famous for; peer-to-peer betting. Whilst the Exchange account won't be closed for winning, there is an additional commission rate.