Thanks everyone, as usual a real mix of advice. Just to clarify a few things though:
In reply to Steph-in-the-West:
> (In reply to yorkshireman)
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> I'm assuming that if you adopted him he's had a bit of a troubled past and would therefore benefit from quite a bit of major TLC
You assume a lot, but the point of mentioning that was that a) he's fully grown now, but b) we haven't had him during the winter so this is the first time it has come up.
His elderly owner died and he was rehomed via a mutual friend. He wasn't particualrly mistreated, but wasn't exercised or trained enough. We've rectified that now (we both work at home) so we give him a routine, he runs with me every day anywhere between 8 and 20km and gets fed good food recommended by the vet. Apart from uncovering a wasp nest a few weeks ago and getting a few stings, he's been perfectly fit and healthy.
> How do you know he's "perfectly happy"? Can you hear him through the night if he whines or cries? and how "little" is his pop-up crate? Has he room to stretch out, curl up, lay on his back, change position?
OK, I believe he is perfectly happy, in as much as it is ever possible for us to truly know how our pets are feeling. The outhouse is hard to explain, but its fully attached to the house and connects to another building we have. Its very large so he has room to run around (its about 15m x 4m) and his crate is more than large enough for him. If anything its too big.
> I've 2 Springer Spaniels, both sleep upstairs with me (in their own beds) and if they need to go for a wee during the night, I can let them out, so they don't strain their bladder waiting for morning or upset themselves by weeing in their sleeping area, which yours would do as it can only sleep confined to a "little pop-up crate."
I should have been clearer. Its not confined to the crate. It has the run of the outhouse (larger than our 2 bed flat in London used to be), the crate is just a popup kennel type thing made of fabric which he can run in and out of.
> Why did you get his dog? Collies are highly intelligent active animals that need a lot physical exercise and mental stimulation - not to mention love and affection!
As I've mentioned, we live in a small hamlet in the mountains, he gets several hours of walks a day (a one hour minimum run, plus a couple of extra decent walks varying in length depending on the day). Both my wife and I work from home so we interact and stimulate him with training as much as possible and he is rarely left alone for long periods of time.
He's an active, engaged, (seemingly) happy and loved member of our household. Since it got cold. he's been sleeping in the house, the reason I asked the question is because I wanted to know if I was being over-sensitive, but so far I'm playing it safe.
I would like to keep his routine (sleeping in the outhouse) if possible as I think this is better for him - but obviously not at the risk of any physical discomfort.