Thanks everyone. It is blooming cold Caryll and started to snow a bit more on our evening walk last night, but it rained in the night and so some of the snow has disappeared.
Stuart - Zak has settled in brilliantly. I was a little anxious to see how Yogi would get on with Zak, as he can be a bit of a bully with some other male dogs, but after a bit of initial posturing and a wee bit of growling (which we quickly stopped) he has been absolutely fine

Really proud and pleased with him. Flame is 10 years old now and a bit of a grump with the other dogs, so she has told Zak off a couple of times, but it is nothing serious and he doesn't seem bothered.
Thankfully all the working pack have taken to him with no bother at all too.
Really pleased all round.