I've posted to UK.d-i-y for possible resolutions, but my question to this
group is if I cut the hedge to ground level will it re-grow? If so is there
any way to remove the hedge to ground level and stop re-growth without root
removal?
TIA
John T

Cut to ground level using a saw/felling axe, or something similar/appropriate.
Any new growth that I presume you don't want can be knocked back by using a
Glyphosate based weedkiller.

Dave.