Congrats on your studio build!

I built my studio in Adelaide South Australia in the backyard and completed it in 2014. It has been really great to work in but I spent around two years researching how to set up sound isolation, sound treatment, hvac, air con etc see https://smartsonics.com.au/ and how I built it at https://jimmyedson.com/studio/

I found two websites that were very useful - http://www.johnlsayers.com/phpBB2/ and Australian based studio designer John Sayers http://www.johnlsayers.com/

I see you are in the UK but basic principles will be the same.

Regards
Jim