Thank you, everyone, for your great ideas.
Baggytrazzas - do not fret! I am currently wearing a sleeveless cotton dress and following the shade around the house… The remedies will be tested in the autumn, when it’s cooler.
Lovebeige - this has been my very unsuccessful method up till now - very frustrating!
Septimia - I had been thinking along those lines, but couldn’t think what would work - I will try this.
Shirley and Doodlebug - sounds like this will work with lighter weight jackets..
Baggs - I have a few (too many) Seasalt tops. I’ve just examined them all and none of them have loops. But I could sew elasticated loops on the inside of the sleeves - that should work.
I think I will try Baggs’ solution first.
Thank you all again for your speedy helpful responses. 