Have you looked at Ocado recently? I assumed they would be unaffordable on a weekly basis on the same way waitrose are for us but I'm so impressed. My first few deliveries were free and since then I seem to get a 20% voucher every week. Loads of their own brand products are comparable price to tesco and they've got some great deals, e.g. 15 quid for 2 mains and 4 extras. There's plenty of obscenely priced products if that's your thing too (5 quid a loaf, anyone?)
I promise I'm not on commission for them but I'm really enjoying them at the moment.