Iirc there are a couple of dive shops in and around Derby a quick Google search will find them, be sure to check what pressure your bottle is and if they can fill it for you. I once had a place close to work but they only filled to 232 bar not 300 bar. 👍
I've had my eyes opened quite a bit this last 12 to 15 months but I guess I'm getting more adventurous in my older years I'm very trusting, but break my trust if you dare