Update 2024: Added two x 13mm Knauf Soundstop acoustic plasterboard with Gleenglue between layers over standard 10mm plasterboard.  All plasterboard edges and holes sealed with heaps of HB Fuller Firesound acoustic sealant, cornice and skirting board redone and finally re-painting.  Lighting and power outlets changed to surface mounted with all cables penetrations sealed with acoustic sealant. Well worth the effort to remove wall and downlight vibrations, lower the noise floor, increased 3D imaging and soundstage, improved detail and texture, and overall sound improvements at all frequencies.