Mark,
had the same bit of confusion so I emailed them, the response was clear.....

my question...........

"Hello,
about withdrawing funds. If I deposit via Bank Transfer from my bank account
to yours for say $1000 AUD. If in 1 month my account is say $5000 AUD can
I organise the withdrawal and transfer back to my bank account of the whole
$5000?
Your explanation of withdrawal is too brief for an important transaction."


and the response............


"Thank you for your e-mail

You are totally correct in the presumption that if you deposited $1000 AUD you can withdraw $5000 AUD. There is no limit on how much you want to deposit and withdrawal with Bank Transfers. Problems would only occur if you use a VISA or Mastercard to make withdrawals as they do not allow you to withdraw more than you deposit.

If you need a further explanation please do not hesitate to contact us.

Kind regards,

Taf Pilgrim

Betfair Helpdesk
info@betfair.com"