You can get this primer from halfords and it is the dogs nads for bare frames.
Spray this on leave it a few days and then wet and dry before using a halfords spray colour. Give the halfords spray a few days to dry and then cut back with wet and dry then a clear lacquer finish.
Cut the lacquer back with wet and dry after a few days and then polish up using a 3m rubbing compound and then a good turtle wax or other polish. I did this lambretta that way last year taking my time and using the halfords paint.
Its much better than the ols holts crap they used to sell and smoothrite is crap now as they had to take all the stuff out of the paint that made it good.
whatever you do dont buy hycote paint it is pure dross.