Ah - I didn't go into details but it turned out that when we went to pick the chickens up (they'd said "they're out the back, we've left them plenty of food and water and we're away for the weekend") I had a good look over them and despite only having seen it in books before I spotted what looked like to me scaly leg mite in 5 of the 7 chickens. Unable to get hold of the owner and knowing they were left alone I took them all home and popped them in an ark she'd had our neighbour make. 20 minutes and a phone call later I was whisking them to the vets for some kind of jab, but sadly it was too late for one of them and we had to have her put down - secondary infection.
So in reply, the chooks spent their first 12 days in the front garden in their ark being move every day on to a fresh patch of grass as we never use that garden for chickens. 4 weeks later and they 'seem' happier, all laying eggs practically every day apart from one bantam who's moulting, and they're now in their own sectioned off piece of paddock out the back of the house, on a strict grazing rotation, so 6 weeks on one patch, 6 on another, then back round.
They are separate from our own chooks until I'm seriously sure they're ok, but as I said, 4 weeks later and so far so good, but I'm thinking long term here - it would be nice to allow them all to mix, so much simpler from a rotation grazing point of view. Plus we've just taken on two new hybrid chooks (a lovely Blue Belle and a cheeky Noir), but the Blue Belle has turned up with a runny nose and sneeze!! I'm doomed to pick up ill chickens. The seller, whose name was passed on to me as reputable my someone who is reputable, has offered a 'swap', but I have this thing where I can't just give it back as I know it'll probably end up on the block, and besides, my daughter chose it, as did my son with the Noir. So it's on a course of Baytril, but so far showing no signs of crusty eyes or diahrroea which might suggest something more serious than a cold.
But...they're both in a makeshift quarantine coop fashioned from a spare compost bin, which is actually working really well! So, we have three generations of chooks here, all at various stages of quarantine...I love the simple life
But when they're all hopefully passed as fit and healthy I'd quite like to let them all keep their current homes if possible, hence the original post
Thanks for the replies so far!