like the bagged salad and fish idea but ideally wanted to ot do fresh food shopping all the time through the week
Do you have a fridge and some sort of freezer?
Frozen fish is really good and often cooks from frozen. Bagged salad will last 2/3 days minimum so it's really not like you have to be doing fresh food shopping all the time through the week.
If you kept fish in the freezer (Morrisons have some really good 3 for £10 fish packs) and watched the dates on things like salad and ready meals, you'd probably fine to shop once a week, perhaps with a top up, or maybe shop something like 3 times a fortnight for 3 or 4 days of stuff at a time, or whatever works for you.
Maybe get a monthly delivery of cleaning products and non perishables, so you only have to look for fresh things when you go shopping?
There's no rule that you have to shop on a regular day each week and buy a full week's worth of food so you can't have things like bagged salad because it won't last. Nor are you restricted to only buying a day or two's worth of food if you eat things like salad.
Fish works really well with cherry tomatoes, so you can bake your frozen fish with these and perhaps serve with some of that flavoured cous cous packets? You can also use the tomatoes in salad (low effort salad - bagged leaves and cherry tomatoes) or as a snack, so you get through all of them.