In reply to LastBoyScout:
I've just bought one of these saddle bags for a two week tour through France.
https://www.apidura.com/shop/
Haven't used it yet but it gets good write ups on various websites, which hopefully justifies the price.
I managed to get a largish sleeping bag, bivvy bag, sleeping mat (tiny thermarest) and a change of clothes into it.
Will be buying the frame bag at some point for the other bits and pieces.