Thanks again. Have just spoken to Express paints about it basically to confirm I need to use a air fed mask. As I will only have to "flat " outside of panels and the 29107 appears to be a good filler anyway think I'll just use that and once ready for base coat do a final block and spray. How thin do you spray your last coat?its 29107
tech sheet is here : http://www.express-paints.co.uk/content/29107.pdf
it states 15 deg, but I've probably been as low as 12 degrees with no issues. it still goes "off" reasonably quickly, but curing time will easily be 36-48hr+ at those temps.
I just use standard hardener, but it might be best to get further advice from those with more experience before ordering, also ref compatibility with your filler
I'm thinking a light coat of epoxy over the flatted filler will allow a delay before base coat. Obviously this light coat will need abraiding before the base