Hi Bryn, I know there's a place over Swadlincote way that a mate of mine has used on a few occasions. I could get hold of him and get the necessary info if that's near enough for you.
Grippers in Swad are sound, I went school with the owner and they did a good deal on a pair of Tourances for me last June.
I had a set of Range Rover rims shot blasted and powder coated for my series 2a a few years back in Anstey, but I can't remember who with. I do remember they under cut everyone else by quite a margin. Probably gone bust since...............
Whoever does the powder coating for you, make sure that they use the correct primer first.
Most powder-coaters simply blast the item then p/coat it. It looks great until it chips, and rust spreads underneath the coating. The subsequent corrosion is far worse than you'd get with a 'normal' primed and painted surface, partly because the toughness of the powder coating prevents the rust from breaking-through the surface. It carries on eating away at the metal.
The lack of primer makes it so much worse.
Sorry for the rant. I could make it a tirade but you'd get bored! Most metal stuff you buy these days is powder-coated (with no primer) and looks like sh1t in a very short time.
I've just been 'renovating' some used PIAA lamps. The shells are in shocking condition - guess what, powder coated with no primer - and we all know how expensive these toys are.