Hi Colin
It’s hard to estimate costs when there are so many determining factors. If walls are already there and plumbing doesn’t have to be moved then that is a great scenario.
Have you by any chance contacted other hot yoga studios in the UK to quiz them? I hope you can get some help that way. It’s often the easiest way and works well if the person you question is willing to divulge. It may be best to ring people who are geographically removed from your intended location.
I used batts in my walls to audio and heat insulate. They were very inexpensive. I used vinyl(?) covered ceiling tiles to minimise mildew and mould. Does that help you?
Let me know where you’re up to.
Namaste
Gabrielle 🙂