In reply to Stew1803:
I good choice of bag, but I agree with @IPPurewater that it would be ok for Spring to Autumn but I'd be surprised if it was suitable for Scottish winter conditions - even mild/lowlevel. I don't think that four season sleeping bags really exist, but putting it inside a bivvy bag should increase the warmth enough. I personally don't like internal liners that as I always get them wrapped around my body.
I have a Xero 200 and its a good, well-made bag for its weight. It is quite snug, though, which can be uncomfortable if you like some wriggle room when sleeping, and it limits the amount of clothing you can wear inside it. The 550 looks to be a similar shape.
I have three ME down bags of different weights and they're all well designed and made, quality kit.
Post edited at 09:43