"Flex N Flat" is a PPG product that dries flat. I've used it successfully on several jets but I don't know if it's available in the UK. Here's a description:
http://www.fycracing.com/graphite03/...17_DCU2060.pdf

Another option for your shiny jets is to rub them down with 0000 steel wool until they are completely dull. Then use a fine automotive finish or "swirll remover" polish and by hand, buff them back to whatever level of dullness you like. I would start with a small area on the fueslage bottom and experiment to see what works best.

Craig