My BiL Dave made a socially distanced visit today and told me about this firm.
https://triple-s.co.uk/He has just had a load of Yamaha RD250 frame parts powder coated in the original gloss black with some parts done in the original matt finish. They arranged for a courier to collect the parts they reported back to him that all was well after they had removed the old paint with no corrosion issue. Parts delivered back by same courrier in bespoke cardboard packs to prevent damage All parts were properly bunged/masked up with superb finish at reasonable price.
They do a special primer coat to prevent corrosion issues with a hot application before the full colour coat & heat treatment.
He is now getting some Gold Finished Steering parts on his Ducati done. They knew all about the 4 or 5 different shades of gold they used at the factory & can match to suit his particular model year.
I suspect others here might know about Tripple S but worth repeating - they don't do gates mainly bikes & other automotive stuff.
They also will powder coat fuel tanks!!