Resilient Bar Foam Tape

For various work related reasons, I never got to fix the Gyproc layer to my studio but I'm now planning to restart the project in September this year. :D So I now have further questions. Would the additional cost of laying 5mm foam tape to the resilient bar be worth the effort and outlay; would I get measurable additional isolation through to the timber stud work?

Not really. Once the drywall is decoupled (via the RC) then decoupling it again won't gain you anything. There might be a very slight damping effect from the foam, but probably not noticeable, and not worthwhile. Save your money (and time!) to spend in places where they can have more benefit. - Stuart -

Brilliant, many thanks Stuart!