Men's Hunt coats are generally made of much heavier material, and will take rain for hours, and still keep the rider dry, but they do get extremely heavy. Lady's, on the otherhand, are made of much finer material, and offer little protection, unless you go for a proper lady's which very few people do, as they aren't as smart. Try Frank Hall's at Market Harborough, they make some of the best hunting wear available
Have u tryed any second hand jackets? I was extremly lucky to be given my Aunts old jacket it is fairly thick and does seem waterproof have been out in some downpours!!! And just seems thru a bit at elbows, does get heavy tho, we wash off out jackets with a hose if they have got v muddy durin the day as well and it the lining stays dry then as well, dint think they make them quite as heavy now though, mine is a caldene though.
I can highly recommend Alexander James- they offer a permatex (like Goretex) lining option for their hunt coats- i bought a lovely navy one 2 years ago and have never got wet shame its now too big but thanks to lovely OH i am having another made in a 12
I have a shires one, the skirt has a a waterproof lining to it, and the whole jacket is sufficiently thick that it takes days of heavy rain before i'm wet!