Hi again – sorry that did not work.
Here’s a thread from the archived forum that may be useful: https://archivedforum2.beoworld.org/forums/p/16661/180744.aspx
To help with the dismantling etc there is a copy of the service manual on the main Beoworld site available to Silver and Gold members.
With regards to the wall bracket, I can’t really help but this eBay listing seems good value: https://www.ebay.co.uk/itm/304457427422