The only way having Virgin broadband can affect a potential BT customer, is if the potential BT customer wanted a phone only service from BT , and wanted the discounted line rental price BT has to supply to customers that don’t want broadband but do want a phone, the rules are that the cheap ‘line rental’ is only for those that want a BT phone service, but don’t have broadband from anyone else .
If you want a BT broadband, having or not having a VM service is irrelevant, if the property has never had a BT type service at anytime in the past , it’s possible that an installation charge would be raised , but generally speaking, if taking a bundle of services ( phone and broadband ) even if a brand new ‘line’ is required, the installation is included in the monthly fee , as it’s ameliorated over the term of the deal,
if the property had an existing BT type line but it’s many years since it worked , then although a socket may exist , the chances are an installation visit would be needed anyway , as everything else would need to be provided again, but it’s not charged for separately, it’s part of the monthly cost.
If it happens to be the case that Openreach FTTP is available, then a new installation would be needed as any previous copper network is not used, again it’s generally not a separate charge for ‘installation’ as you would be committing to a minimum term contract, the installation costs are covered by the monthly fee
