I would like to recommend Le Petit Vapoteur
https://www.lepetitvapoteur.com/en/, a french supplier.
If you sign up, and are signed in, UK customers get tax free prices which are very competitive. The range of stock is very good, they frequently have discounts and their loyalty scheme gives you 1 euro for every 10 euros spent on your next purchase. Shipping is free by courier for purchases over 30 euros, and takes 3 about working days. I've bought loads of stuff from them and never had a single problem. My only worry is that when we leave the EU we might lose the tax free pricing.