Here are a few things I have as storecupboard ingredients for veggie food, it may be useful for you.
I find a lot of my homemade veg bakes, soups etc are pretty bland initially, so a good stock or flavouring really helps.
I like Marigold vegan bouillon powder, pref. the one in the green tub. It has a little TVP
https://www.marigoldhealthfoods.co.uk/bouillongravystockcubes
Some of the Umami products add a depth of flavour. I like this one, a dessertspoon will liven up a whole family sized portion.
https://www.ebay.co.uk/itm/156581483064?
Dried Porcini mushrooms are a very handy thing to have, they add a wild mushroom taste. All you need to do is put a dessertspoonful or less in a mug or jug. Add about three quarters of a mug full of really boiling water and leave to stand for 15 minutes. That gives you mushrooms and stock.
https://www.tesco.com/groceries/en-GB/products/317298381?
Tinned lentils and tinned chickpeas in water or brine are handy to bulk out a main course. Some recipes use the water from the tins too, so do check before you strain them and throw it out.
Oil for cooking or salads, try and get the best you can afford, there's quite a lot to read up on online to help you make an informed choice.
Frozen veg isn't usually UHP, also make your own, cook twice as much veg as you need, then bag and freeze whatever you didn't use that day.
Soon you will be able to prepare a veg dish using your own frozen veg, easier than peeling and chopping it from scratch. I have my own green beans, tenderstem broccoli, carrot swede, parsnips, other root veg.
Potatoes and sweet potatoes boiled, roast,
Bought petits pois as ND dd likes those not peas. Bought M+S frozen Chargrilled Meditteranean Veg, it contains sliced courgette, aubergine, red and yellow peppers. I thought it must be cheaper to make my own with the same M+S fresh veg, but I had a go and found it was quite a bit more expensive for ingredients let alone cost of oven to roast them. And the packet ones are easier to use. Mine which I layered on baking parchment were not easy to separate.
Nuts and seeds are again great to add protein. Aldi and Lidl are probably the best place to buy them for good value. Buy the ones without shells but that still have the inner skin on. Ignore the ready chopped or flaked or ground as they are not as fresh as the ones you do yourself.
There are lots of recipes online for nut dishes that need no cooking. Check out Deliciously Ella, many of them use Medjool dates, coconut oil and Cacao (not cocoa!) powder, so bear that in mind if you are feeling creative.
Vitamin D for immunity and Vitamin B 12 because its only source is meat are worth considering.
Please take on board anything that appeals and ignore the rest.
Good luck with making and eating healthier food, if you lapse, don't worry, just try again the next day.