My partner is Vegan, so I can't use milk or butter but she has sent me on a quest to make a vegan naan. I'm no idea if this is possible or will lose the texture of the naan by making a vegan naan.

Does anyone have any ideas?

Type vegan alternatives for milk, butter etc into Google, this should help you.

I've made many a vegan/allergy friendly meal - and it is possible to do quite a good job without losing the texture/taste that is desired.

I'm not sure if Earth Balance has made it over (it is a product sold here in the states) but it works really well.  Vitalite is one product that I know is made with sunflower oil and is vegan, and AFAIK is available in the UK.

As far as milk, plain (unsweetened) soymilk/almond milk/coconut milk do a great job substituting.  It should be fairly easy to find these, I presume.  Maybe already in your fridge.

Some Naan recipes I've seen call for eggs - there is a product called "Egg Replacer" made by Ener-G.  Works great.

I actually believe I made a Vegan Naan bread at one point, though I don't have a specific recipe.  I just simply adjusted the ingredients on one of my existing recipes and it turned out great!