Posting here for maximum traffic.
I got an email saying my account was suspended due to a third party attempting access. I contact Betfair who tell me that attempts were made from multiple locations and I don't have a balance. I hadn't used it in a while as had put Matched Betting on hold and I can't quite remember how much was in it. Just a warning to anybody else to check their accounts.
They say there is no evidence they have been hacked - but they must have been!