Unfortunately I am coming to the conclusion that this is one of those unique configuration problems, and unless it is possible to pinpoint the exact issue it will never be resolved. The likelyhood of anyone having the exact set up as me is very unlikely.
I have checked the firmware, The BT Home Hub has the update that was released last month (I didn’t install it, it must be an automatic update) and there are no updates for the Belkin.
I did actually think I may have stumbled on a solution last night, but it turned into a red herring. But interestingly it did change the behaviour of the Soundbridge, but for the worse. I switched off the Hub built in firewall and the Soundbridge connected without a restart, it played for an hour then lost its connection as usual, but even a restart wouldn’t reconnect it, it lost internet radio access, it couldn’t even set the time, although it did say it was connected to the wireless network at 100% where usually i am getting about 70-80%. It wouldn’t even connect direct to the Hub it just says no DCHP received.
Hopefully, this morning, I can put it all back as it was! 🙄