Since the recent enforced switch from copper to fibre Virgin has compromised my phone system, which is based on twin (expensive) Beocom 6000 wireless phones. I can make outgoing calls as usual with them but with incoming, they do not ring and callers are quickly disconnected, or else told the line is busy.
Not doubt you have searched for past topics on this forum and found the past mentions of problems with the Beocom 6000 phone. Similar issues have also been mentioned on the BT forum. As far as I know, there has not been a solution to the problem that I have come across. It seems to be a particular issue with that phone model and other B&O phones.
The non-ringing of phones post-switchover to the hub is caused by there being no 'ringing capacitor' in the hub's phone connection (whereas there is such a component in the traditional telephone master socket). This issue tends to effect older model phones (generally early 2000's and before).
Some people have reported success with this type of adapter in getting old phones (in general) to ring
which is a 'RJ11 plug to BT socket adapter with ringing capacitor' and can be bought online (from other suppliers too) for just a few pounds. This single adapter is doing the same thing as the ADSL filter+VM adapter combination you already have set up by providing a ringing capacitor.
The adapter will NOT fix the problem with the Beocom phone, most likely though (just reduce the number of adapters for you). No guarantees it will help with your backup phone ringing here either so use at your own risk if you decide to buy one.
One of the last topics I replied on about this was here
It does contain a bit more background info but no fixes, unfortunately. No further update either on whether the OP on that topic got the Beocom phones to work on a new BT line. I would be doubtful as similar problems are also mentioned on BT user forums.
All suppliers are now using phones-via-router to supply customer landlines, and traditional telephone landlines are no more, so the same issue may persist even with a different supplier.