I've gone back to being a Santander customer again, although I suppose I never properly left - we've had a cash ISA with them for a pretty long time now. Their 1-2-3 offers on both current account and credit card seemed too good to miss, and so I have obtained both. The current account comes with a selection of cash-back on various bill payments, as well as an appealing interest rate on credit balances, and the credit card comes with various cash-back deals at different shops, as well as 0% interest for 18 months. And, to clinch the deal, the rather rubbish rate of interest on the cash ISA that we have been getting up to now gets considerably better because we are current account customers with them again.
The plan is to load up the credit card during its 0% period, and rather than pay it off each month, leave the equivalent amount in the current account (or the ISA) earning interest. Overall, through a combination of cash-back and interest, could turn out to be world £50-100 per month.
The only temporary frustration is that whilst the credit card has arrived, I haven't been able to activate it yet, but hopefully a quick phone call tomorrow will sort that out (as well as a quick trip in to the branch sometime soon to get them to issue me with some new internet banking logon details so I can keep an eye on things).
Splendid - next money-saving plan is to sort out changing our energy supplier from the one we inherited when we moved in here to one with a cheaper tariff.