You looked into the gtechniq ceramic coating life?! Worth a punt..
Yes, Gtechniq sent us several different products to test on the surfaces we work on. We work mainly with fibreglass and plastic, plus enamel coatings, and these products are better suited to painted and lacquered surfaces for several different reasons in my professional opinion.
I did test it on my wheels and roof of my T6. The roof showed good results, but then so did other products we test, but the wheels were a disaster. They were freshly powder coated, and the product dulled off the finish, and this is not an isolated incident from what I read.
All these services are only really as good as the application, preparation and aftercare, so if I had to use this type of service, i'd probably use an independent company, and not a huge dealership or a company that turns over dozens of these jobs a day.