I'd check the bank first to actually make sure that they HAVE taken the money.
Normally Direct Debits are taken on the first working day around the actual date. However, my company updates customer accounts with the direct debit information a week early, but does not physically take the money until the due date
Got a Letter Today (the day the direct debit should have been taken out) Stating due to a "technical hitch" virgin media system took the direct debit out early. anyhow the direct debit wasn't taken out twice.