Very interesting story.
I have a similar issue on a plot of land I have recently purchased.
I am after a 100amp SP supply on my land and the closest available mains for me to connect to is an overhead HV line about 120m along a country road.
UKPN have quoted £27k to connect to this which includes a road closer on the lane and running the cable through just over 100m of road. This is way out of what we had budgeted and now considering selling the land! Surely it would be cheaper for them to install another pole closer to our plot and not have to dig up so much of the road?? We do also have permission of going through a neighbours field to another pole 400m away which is right on the edge of their field. We thought we could install the cable running through the field to save costs. Then we would only need UKPN to connect the other end and install the meter on our property. Would this likely be cheaper?
Any help or ideas with this would be much appreciated as we are losing hope. Our budget for electric was £10k and we thought it would be more than enough!