OK, I'm totally convinced now I have just ordered some vintage raw denim purchased cheaply off a local auction site to use for the sleeve lining in lieu of cotton drill proper. It's probably unsanforised, so I'll give it a soak first. I hope it will do. It's not very heavy (more of a shirt fabric rather than trouser material), probably the sort of weight Aero uses for their jackets.
Many thanks everyone!
Many thanks everyone!