Depends, Scotland's weather is so changeable, where are you planning on going ? What are you sleeping on mat wise, thermals will give a big boost to warmth if needed for little space and weight, a bit more info may help.
We're going to the Glencoe region it's our first time to Scotland were hiking with another couple so the guys can take the heaviest rucksacks were using roll mats and also have the orange survival bags to cover the sleeping bags we hope that will keep heat in if the weather is cold we will only be 5 or so km from our cars
The orange survival bags are really just oversized orange bin liners and you'll sweat more than a weight watcher in a cake shop waking up damp...better off with an army Goretex bivi bag which don't cost the earth off ebay. That said a fleece jacket and loose fitting socks will keep you toasty in your sleeping bag.
As @Harry Palmer says, your better off without those orange survival bags and go with something that's breathable, of the temps dip you'll wake up child and damp, I don't think the roll mats alone are enough, some sort of inflatable mat on top of it, preferably insulated but it's down to cost, what sleeping bags are you using.
Reminds me of an incident many years ago. We were down the new forest area and the weather ally pleasant . So much so that we decided to sleep out in the open. Sod's law , there was a rain shower in the night and we made a hasty retreat to the van . Next night we thought we'd try again but my one friend wrapped his sleeping bag in bin liners. We woke up next morning all fine and dandy but he woke up sopping wet. Childish but we did giggle.
Talking of hiking in scotland it's a grannies and eggs thing but I'd not go without waterproofs and even if rain isn't on the cards I'd still want my gaiters if I'm likely to be walking through long grass early on in the day.
As @Harry Palmer says, your better off without those orange survival bags and go with something that's breathable, if the temps dip you'll wake up cold and damp, I don't think the roll mats alone are enough, some sort of inflatable mat on top of it, preferably insulated but it's down to cost, what sleeping bags are you using.
Glen Coe is midge central so SMIDGE is an essential part of your kit. Cover all of your skin with clothing, including gloves and a hat with a midge net. I don't imagine you'll want to do the naturist thing up there!
And as others have said, in all likelihood you'll need waterproofs at some point.
Gaiters may also reduce the chance of ticks latching on.
If you do use the orange bivvi bags be prepared to be woken up by every passer by enquiring if you're alright, some of them will have made a detour just to check up on you. Most people assume that the orange bags are emergency kit. I've only ever used them during DofE awards as a teen.