As I said in my presentation here, I'm so much of a newcomer that I haven't taken my OWD course yet (it's due to start in two weeks' time).
I was glad to see this thread here, as what to wear between and after dives is something that has always puzzled me. And that's something that may not be mentioned in the course!
I assume we'll be using a drysuit during the course, maybe with some other layer below, depending on the weather (I have no idea how cold or warm the Mediterranean will be in early October, though I expect around 20ºC outside the water). We'll be doing two dives one after the other, and I had always thought we'd remain with the drysuit on between them, maybe with a windbreaker or a polar fleece on top of it if the weather is cold (suggestions?). And I had also assumed that we would be wearing that on our way back, too, and get changed someplace on land.
But reading what you've written, I realise I may be wrong. It seems much more complex. I never wear skirts, dresses or pareos, I loathe shorts, and I'm the type who wears a T-shirt and jeans all the time. So this is the sort of stuff I'd have to change into.
I had assumed that once on land, I would just put the T-shirt and jeans on over my half-wet swimming suit (a full one, since I've never been keen on bikinis), and go to the hotel and change into completely dry clothes. But if that's not possible, I suppose I'll die of a severe cold sooner or later, from walking around all day with a wet swimming suit on.
But now I realise I may have to change clothes on the boat. The type of boats I've seen in the photos and videos from the diving school I'll be attending have no sort of toilet or private place, and at some point I suppose you must go stark naked so as to put a dry bra and knickers on, mustn't you?
Funny how I hadn't thought of all this before!