I mean this sort of thing!
Practically, that might mean either a form of pot where the balance is offset against loans. Simply put, if you have £1000 in an offset pot and £1000 on a credit card then you wouldn’t pay any interest. Similarly, if you had £700 in offset pots, £500 on a credit card and £500 overdraft you’d only pay interest on £300 (although naturally this would only apply to credit card spend after the interest free period).
Ideally, you’d be able to make the whole account offset. So the whole current account and pots would offset against borrowing costs.