Nick,

Thanks for the pics. Yes that's a good option for an existing wall.

originally I had come across these brackets that would bolt to the stud on an existing wall. It looks good but they are only rated for 15kg's so no good for any Meridian speaker.

[Linked Image from ecx.images-amazon.com]

[Linked Image from keene.co.uk]

Theatre Room: Sony 4K VW500ES, 861v8+ID41, HD621, DSP6000's, DSP5000C, DSP5000's, Oppo 205, Sat STB, XBox One X, Stewart Cinemascope Screen, QNAP TVS 1271U-RP (96TB) with Sooloos/Roon core pkg.