Bobloblaw, Wiccaweys are a VERY good Collie rescue and theyhrehome across the country. Wiccaweys
Many Tears also rehomes across the country and is an all-breed rescue which has an awful lot of Collies and collie crosses - I've just seen some beauties on their website.
Heathlands are in North Herts and also rehome all breeds but in particular Collies, many of which they save from certain death in Irish pounds, where a dogs chances of survival are even worse than here in English pounds.
Flightattendant, you sound like a lovely person to own a dog, but I wouldn't recommend a Collie to you at all. They need a lot of exercise and mental stimulation and are likely to become bored, miserable and possibly even destructive or temperemental without a heck of a lot of human input and chances to run. There are LAODS of other breeds and crosses which would suit you though, I'm sure.
Funnily enough, and although you might say ARGH! or UGH!, a Greyhound which is small animal friendly or a Staffie might be ideal. Both are affectionate and sweet natured and do not require as much exercise as a Collie.
WRT going to Tesco, I'd suggest establishing crate training from the off and popping pooch in there with a Kong and fresh water if you're going to be out for just a short while. Whatever you do, don't leave your dog outside the shops - it's a recipe for disaster, just asking for some b888888dto steal your dog or mother to complain that he looked at her PFB and therefore must be put to sleep.
Oh, and PS, I want to live in your house! I adore pigs but I think my Landlord might have something to say about me adopting one, and I'd would love to have chickens, dear little things, but my evil killer cats would terrorise them!