I totally agree with pp who said use dried pulses where you can instead if quorn - it's so much cheaper bit fartier though and you can do them from dry in a slow cooker if you have one, then portion them into tins-worth in bags and freeze, then just pop it back in slow cooker with tomato paste etc to cook if you like pasta sauce/ curries/ chilli etc. A 400g tin is about 250g drained weight and I used to get them 3 for £1 at Asda until I sussed out the slow cooker thing - a 500g bag of the dried stuff makes 6 - 8 tins-worth and slow cooker uses same electricity as a lightbulb, compared to gas/ electric hob it's definitely cheaper. If you live anywhere near an international supermarket you can buy a lifetime supply massive bags for a couple of quid.
Do a massive batch of general tomatoey sauce the freeze in useful portions.
When you come to use it, transform it into bolognese (add oregano), chilli (add chilli powder etc), curry (add curry powder) etc.
Frozen veg is often cheaper than fresh and none the worse nutritionally, look out also for frozen garlic and herbs.
Reduced price/ special offer veg in a serviceable condition can be prepped and frozen. I've saved fortunes buying party packs of bell peppers and mushrooms or Aldi super 6 and chopping it all up, cook with what you need then freeze the rest - no waste that way either.
Save all your marg/ ice cream tubs for use in freezer (stackable and easy to write on with a marker so you don't end up with Anonymous Brown Stuff and no idea what it is because everything smells the same when it's frozen). You've already paid for them, unlike freezer bags. Ditto jars to reuse for things like bags of cupboardy stuff so you can see what you've got and not buy stuff you've already got.
Make your own pastry for pies, jam tarts, etc. Do a shitload and (you've guessed it) freeze them. Defrost, add hot custard, cheap puds.
Make your own soup - tastier, cheap and again, freezable. God I hope you've got a freezer after all this...
Grow your own culinary herbs.
Use tomato paste and water instead of tinned toms/ passata.