You should try carrying all your stuff on your back over the top of a bunch of Munros. That will teach you to pack light...
Actually I have been through a pretty similar learning process to FF.
Bear in mind that I own warm base layers anyway due to also enjoying being on top of said mountains in the middle of winter (not camping, though). Also cold is more of an issue when you are camping high. So, I carry my warmest winter base layer instead of a second fleece; and I sleep in a mid-weight thermal top and longs set. A fleece hat is always in my rucksack whatever the time of year and wearing a hat in bed is a good thing. Some of that might be useful if you feel the cold when you sleep.
I'm also a fan of Alpkit - I have a down sleeping bag from there, and a headtorch, and some dry bags. (Everything goes in drybags on the hill).
I have a really mini Trangia and my luxury item is a kit that lets me use my Thermarest as a chair.