Bullion By Post
Hatton Garden Metals
are some of the most well known and I have used them all myself so I can vouch for them.
New coins will attract VAT unless stored outside the EU in a secure vault.
Pre-owned coins are VAT free.
You can also avoid VAT by buying from a European dealer like Goldsilver.be. I bought some silver from them several years ago to do this. Not 100% sure if Brexit has impacted on this option now though.
If I had £2k to spend on silver I would buy a slabbed and graded coin like