Does anyone have any idea who I could contact to find out if there are plans to get around the issue?
From the very text you posted:
"This marker shows cabinet: P39
Which is linked to exchange: BARNET
Please note: This is the intended area for the cabinet that will provide fibre broadband services to your postcode. Unfortunately there are other underground utility services in the approved location for this cabinet. We are seeking an alternative location.
When we plan where to locate a cabinet it is done on the basis of underground utility records (for example gas, water and wastewater) available to us at the time. It is rare and unfortunate, but in the case of this cabinet the records were not complete or incorrect and we cannot install our cables in the position originally planned. We are therefore looking for an alternative solution but this will take some time
. We are sorry for any inconvenience this has caused."