I think we will probably try the masking up and varnish route, none of the paintwork looks damaged, it's just the blue in that area goes chalky when it rains! That's after a divvil of a job when washing it.
We have all the good wash and polish stuff, no wash up stuff has ever been used...haha.
Dhutch, the paint used for the coach lines is the same light grey that is on the none slip roof, it is not shiny.
Well I'm pleased I asked the question as now we can try a few things out, might help someone else too!