Panic over, I found a length of webro HD100 on ebay complete with 2 F connectors. Also bought a load of speaker cable so I can re-arrange the 5:1 speakers to suit the new room layout, with fresh cable - the existing cables are all battered because they've been moved so much. And an optical cable because the current one is only 0.5m long and restricts where I can site the 5:1 controller in relation to the BD player.