"After being told contradictory information by BT customer services, it transpired he was not eligible for fibre broadband because the cable only went to the cabinet - and not to his home."
Yes, that's the way that BT Infinity works, they have an optic link from the exchange to the cabinet, then VSDL over copper from the cabinet to your home. Nothing said there precludes BT from providing him with a faster connection.
The problem is that if you're more than about 800m from the cabinet then VDSL slows down to similar speeds to ADSL2+, so it's only useful for short runs. This is OK for urban environments, less so for rural.