Just by way of an update, the bees stayed, they have built out around 15 bars of comb in my TBH. It has not been plain sailing though, because they didn't want to build the comb straight and I've had a few problems trying to sort it... however I am getting there. I took a tiny bit of honey yesterday which was really delicious.
I've learned so much and gained confidence working with the bees, so its been a good season for me. I hope to build a second TBH (haven't told the OH yet!
) for swarm control / expansion next year. I'll change my bar profile to a deep "v" or perhaps waxed foundation strips (which I have had success with here), but definitely not a waxed saw kerf!
All my notes and photos are documented
here