We have old sash windows with rotten sills. I've made good the wood using
wood hardner and filled with filler etc etc and now have a presentable
finish.

However from past experience I find the paint cracks after a while betwixt
wood and filler. Googling around I discover Latex Gloss Paint is
recommended - however I think this is a US product - do we have anything
similar here in the UK??

Failing that whats the best way to go about getting a lasting no cracks
paint finish with glass fibering etc etc?

TIA

Grant