Certainly one of the more interesting and unusual accounts related on here. I imagine the exact details of everything are more involved than as they appear in this topic. I'm not aware of any particular general topic on here regarding switchover issues and OFCOM.
If VM has provided you with a deadlock letter, you have 12 months in which to take that to the ombudsman. But the ombudsman can't compel VM to install a landline for you nor go back to a conventional landline arrangement AFAIK. The ombudsman could assess the compensation offered if that is unsatisfactory to you.
VM's offer above seems to have covered the options that I am aware of (including an option to cancel services and a technical option to rewire). There is a clause in the compensation scheme which may limit compensation if the customer 'prevents the service issue from being resolved'. I imagine VM may possibly cite the offer to rewire the connection as part of that if it seeks to limit compensation.
If you move to another provider though it is highly unlikely you will get a conventional landline installed. It will very likely be some variation of a phone-via-router connection in some form or other.
The fact this has dragged on for so long seems very unusual.
Has VM ever managed to provide a working landline connection via the VM hub (even if the hub is not in a suitable location)?
VM's rewiring options generally seem to involve moving the hub as a first choice but they should also offer reconnecting existing telephone extension sockets in the home so the hub did not have to move if the hub location is a sticking point. That, however, also might involve some rewiring of the extension sockets.
You should probably contact OFCOM in regards to what extent VM has to go to in order to provide an emergency connection. The EBUL phone is their default offering but, if it does not work in your home, then it won't be much use. I wonder if there is some means of connecting an external aerial to the EBUL unit to place the aerial outside, via an aerial extension cable, and the EBUL inside in an accessible location or some kind of mobile signal booster. An alternative battery backup for the VM hub may be of limited use when a power cut extends to a wider area as the connection may still not work.
You should perhaps speak to OFCOM to establish what the limits of the provider's obligations are for emergency backup when the local mobile signal is poor.
