Dan, if you do travel up to Scotland you're welcome to get in touch, if you want, to meet up, just send me a PM.
Winter is definately here! Temps here at the moment are just above zero, Monday and Tuesday last week were circa -8°.
I've been up here for 17 years, originally from Dorset, in that time the coldest it's been, at about 800' above sea level, was -21°, lovely clear blue skies and still. I had a friend visiting around that time and he went to start his car one day at about 11a.m. and couldn't believe it was -16°. My lowest camp out temp. was at a friends birthday bash where a few folks had said they'd camp out, in the end I was the only fool left outside at -18°, not a bad nights kip but, 1) I had previous experience, one of the reasons for moving up here, and 2) I was properly equipped!
As others have said, It really isn't the place to start off with in the winter, I had some truly awful nights camping in the winter in Dorset when I was a teenager, inexperience and very, very basic camping equipment being the causes, I'll bet the kit you've got is better that what I had then though!
I'd recommend spring and autumn for your first trip up here, nowadays I very rarely camp out in the summer, I just leave it to others to feed the midge's and ticks!
There's some lovely places near you to get out for a night or two, take what you've got, don't go too far from your vehicle and find out what works for you, or doesn't, enjoy yourself and be safe.