Hi John
I wouldn't give up on Scottish sources of bees so easily. I could name one or two that I know I could trust. You'll have the same issues with bees south of the border - some excellent suppliers of healthy bees, some more casual and even some that folk say should be avoided at all costs. The problem is knowing which ones of course.
There is even a supplier right in the heart of the worst EFB area to the north of me who has supplied bees to beginners around here. He has been inspected and is clear, and the beginners bees I've seen from him are fine too. Not that I'd recommend taking bees from central Perthshire to the far SW of course.
I'm not sure what the types around your area will be, but in much of Scotland mongrels with a strong tendency to native types predominate. Introducing Carniolans might be a pity - they are likely to be very swarmy (people say!) and the hybrids down the line may make beekeeping difficult for you and others in the area.
Interesting that you used to have lots of ferals locally. Other parts of Scotland seem to be hanging on to some ferals, although the one in the castle near me died out last winter and was recolonised last summer.
best wishes
Gavin