I assume you mean August, not April. Apart from that you are right that there's a very high risk that you will be left without a connection. Ordinarily, connecting VM in flats and other shared ownership or apartment rental arrangements is complicated enough due to the permissions required and agreement to cable routes and the like. This is made vastly worse at the moment by what might politely be called "operational difficulties" in the pre-installation part of Virgin Media's business.
It certainly is POSSIBLE that you'll be connected on the due date, but I have to say that regardless of any assurances from VM you should plan for the worst whilst hoping for the best. So planning for the worst means either seeing if you can defer the cancellation of the existing service for a month (and maybe more), or seeing if you can create a workable wifi hot spot arrangement with your mobile phones. Hot spotting can be a quick and easy solution - assuming you can live with the data used, but if this is your Plan B, set it up and test it before you need to rely on it. And make sure you keep an eye on data use - you don't want to fall foul of any unreasonable "out of allowance" data charges, or if using PAYG you don't want to be participating in an online meeting and suddenly be cut off because you've used up all your data.
