thanks all.
Prior to posting today, I actually did just that! (I didn't expect a response from the Council today, let alone how things have progressed!)
Finally, some action is being taken.
I logged a report with West Northants Council...
they told me to call Balfour Beatty...
after a call and some emails back and forth to them (who I must say, were VERY helpful!), Highways were contacted and so were Virgin Media (who previously denied all knowledge of this cabinet) by Balfour Beatty on my behalf.
Within an hour, Highways "made safe" the cabinet by surrounding it with those red "roadworks" gates, VM Engineer turned up about half an hour after and has apparently logged a job to get it dug out entirely.
Fingers crossed the last part actually goes ahead sometime soon.
Either way, I'm quite happy.
Thanks for your replies!