IMO there is little or no difference between veggie and non veggie cheddar in effect, it's definitely available in ASDA so is probably available in the other big supermarkets - just check it has the "suitable for vegetarians" message/tick.
I've just checked the Waitrose website and they have oodles of veggie cheddar. I'm sure you won't have a problem finding something in Morrisons or Tesco.
Many regular cheeses these days are vegetarian as veggies are a big audience for cheese. It just means they use a vegetable rennet to curdle it instead of boiled up animal stomachs. Check labels of your regular cheese options first.
If you are cooking for a vegan that's very different. The 'cheeses' are usually made from soya milk and you would be best to practice your sauce making with it as they can be tricky when you start melting them.
Would have thought large stores would have vegan cheese - otherwise Holland & Barrett.
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