I agree re the fish - if I'm with my mate in Saffron Walden on a Saturday I'll generally go to the market - there is a fantastic fish stall which drives in from Lowestoft Everything super fresh - lobster, monkfish, oysters, crevettes, langoustines, crab... I've several times bought lobster just because I couldn't resist.
Recently - I think this may be since son turned vegan, I've more or less stopped planning meals altogether. I order on-line lots of vegetables plus tofu and some soy meat substitute. I always have lots of tins of beans and dried pulses, rice, pasta etc. plus a very full store cupboard. So - most days I'm improvising. Its easier to do this if you don't buy meat or fish because veg tends to keep much longer and even if it goes a bit mouldy you can cut the mouldy bits off!
Currently I have cauliflower, long red peppers, potatoes, sweet potatoes, carrots, golden beetroot, mushrooms, aubergine, asparagus and about 18 eggs (me and daughter eat lots of eggs). Also blood oranges, apples, plums, raspberries and grapes. I've no idea yet what I'm cooking for tonight from that lot.
But there is a spur of the moment purchase I made yesterday in Aldi - it must a reaction against veganism because I found a 28 day aged sirloin steak in my shopping basket.