Standard VM response is the 'council permit' excuse. You need to do some brushing up on the compensation scheme and start putting together your evidence for a case to arbitration.
Link below is for OFCOM's minimum requirements document for the compensation scheme
https://www.ofcom.org.uk/__data/assets/pdf_file/0026/216962/Industry-Code-of-Practice-for-Automatic-...
Para 40d gives one of the reasons VM might reduce a compensation payout (not remove it completely).
For example if VM, or its contractors, is kept waiting for 2 days for a council permit to work, then compensation might be reduced by 2 days. What tends to be reported on here is that VM tries to blame the whole of a very long delay on the council. It would be unlikely (to the point of impossibility) that the whole of a very long delay could be blamed entirely on the local council. VM's contractors are agents for VM so any construction delays involving the sub-contractor are covered by the scheme (and also note para 41 above).
The reality, which has been retold in past topics on here, is that permits are often issued quickly but general bungling and delays by VM and the contractor mean the window for the permit expires before the work is completed and so another permit/delay is required.
Some savvy customers, in past topics on here, have contacted their local highways authority to ask when permits were applied for (when VM was playing the 'council permit' card to avoid paying) only to find that no permit was ever requested by VM and its sub-contractors.
So, depending on how you feel about pursuing the matter, you next steps would involve building your case to go to arbitration.
This would involve creating your own timeline of the project with all VM's failed promises and delays mapped out in detail.
Your should also contact your local highways authority (which might be your local council or county council depending on where you live) and find out from them when VM requested permits to do your work.
After that, you would need to make a formal complaint to VM (a required first step but likely to result in a fob-off reply). After that (8 weeks later or with a deadlock letter) you can go to arbitration.
https://www.commsombudsman.org/
The prospect may seem a bit daunting and unwelcome after a long wait but VM's patterns of behaviour, in similar cases like yours which have been described on here in the past, relies on grinding the customer down until they give up or accept a much-reduced pay-out.
There have been a few topics which have fed-back good results when the customer has complained to the ombudsman and obtained meaningful compensation when VM originally said it would not pay or would only pay a much-reduced sum compared with the scheme's provisions.
Have a look through some past examples which might offer you some encouragement (some are for fault/repair compensation others for installation compensation)
https://community.virginmedia.com/t5/Managing-Your-Account-Cable/Compensation/m-p/5375731#M236832
https://community.virginmedia.com/t5/Home-Phone/A-tale-of-woe/m-p/5345224#M194067
https://community.virginmedia.com/t5/QuickStart-set-up-and/Compensation-advice-please/m-p/5326587#M2...
https://community.virginmedia.com/t5/Managing-Your-Account-Cable/Compensation-Scheme/m-p/5304899#M22...
https://community.virginmedia.com/t5/QuickStart-set-up-and/Compensation-awarded-by-CISAS-after-faile...
