Question: Although we can't afford true Fibre, can VM utilise this cable to provide their traditional coax-based service, by converting the fibre on-site.
Sadly no. That fibre will be going to some metro-Ethernet kit somewhere which is no good for CATV, and VM wouldn't install a fibre optic node in situ even if there were a viable fibre route.
They aren't going to devote an entire optical node to just your premises either unfortunately. It would actually be more expensive to them than a leased line.
They can't run coax from half a mile away, they'd need to use too many amplifiers and the signal wouldn't be much good by the time it reached you. That or use insanely fat coax which mightn't be an option.