You might want to investigate foam board insulation for the walls:
http://www.homedepot.com/b/Building-Materials-Insulation-Rigid-Insulation/N-5yc1vZbaxx


Foam board insulation is flammable and code here says we have to cover it. I have it in my basement and it really helped. If you also have to cover it you can use paneling. I used 1/2" (31.75mm) foam board and it worked.

For the ceiling You might want to investigate 2"x6" (50.8mm) studs, 6" (152.4mm) fiberglass insulation covered with dry wall:
http://www.homedepot.com/p/Owens-Corning-R-19-Kraft-Faced-Insulation-Continuous-Roll-15-in-x-39-2-ft-RF40/202585898

This should keep the room warmer.

FWIW I would solve the heat loss problem first then attack the acoustic problem second.

PS - I am assuming that all of the products that I mentioned are available in the UK.


Back in my day the only time we started panic buying was when the bartender shouted "last call"!

64 bit Win 10 Pro, the latest BiaB/RB, Roland Octa-Capture audio interface, a ton of software/hardware