The contact info which used to appear for this has been getting gradually removed from past topics on the forum. There have been quite a lot of enquiries about this sort of project in recent months on the forums. One can only assume VM are seeking to avoid any involvement in this kind of work and are making it difficult to make enquiries. Suspect you have been using the correct 0800 number but it is not being managed reliably.
Default procedure seems to be, you pay VM a survey fee of £240 and they then produce a quote for the work. The only past example I can recall with costs mentioned is here
https://community.virginmedia.com/t5/Managing-Your-Account-Cable/VM-manhole-cover-in-new-drop-kerb/t...
It may not offer you too much encouragement if it is a typical example.
One of the VM forum team should respond here in a day or two and should be able to advise on the correct/current procedures and costs, most probably via PM.