I have had a reply back from the bank re: paying off credit card bills early. This information may be useful to others.
"If you pay the full balance off at least 5 WORKING DAYS BEFORE your payment is due, then the Direct Debit will take nothing. However if you pay the full balance off within 5 working days of the payment date, the Direct Debit will take the funds again".
What is a reasonable minimum spend for an online grocery delivery??