Check out City Powder Coating in Digbeth, Birmingham. They have a website.
www.citywheelrefurbishment.co.uk
I have had multiple sets of wheels powder coated over the years and vouch for their work.
If you can get to them then you can look around the showroom to locate the colour you want.
3 options....
1. You give them the alloys without tyres
2. You give them the alloys with tyres
3. You drive in with wheels fitted and they do it all in the same day
Check the website for pricing but last time I looked it was 1=£20, 2=£30, 3=£40 per alloy
They can also repair cracked alloys. Or road marked alloys
With the same spidery corrosion occurring on our small Audi, I will be having the alloys powder coated very soon.
Update: I have just checked the website. Prices per alloy have increased by £5, so 1=£25, 2=£35, 3=£45 per alloy