VMG8924-B10A VoIP menus removed by ISP

Hi All,
Just opening up a new thread on the missing VoIP tab in a VMG8924-B10A. I recently moved to John Lewis broadband and although they now only provide a VMG3925 router for new customers, I wanted to use VoIP so got hold of an 8924 only to find the VoIP stuff missing. I did try downloading and flashing with the latest firmware but still no VoIP tab. I notice that there are two files in the firmware zip file, a .BIN file which is the firmware but there's also a .ROM file so I wondered if that might contain the stock menus that have been knobbled by John Lewis?  I would have hoped that the actual router hardware is standard and it's a software/firmware hack that John Lewis have used to disable VoIP configuration.  
There are some sections in the backed up config file that relate to voice stuff but it doesn't look too easy to figure out what fields to edit to use my two Sipgate accounts (no SIP account number or password fields for example).
Has anybody managed to get one of these routers back to its factory (non-ISP) state so that VoIP can be used?


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