I have two cables coming into my house. One is from my current provider (Virgin) and the other is an obselete cable from a previous provider. If i again changed my broadband provider is it possible for them to use existing cable(s) or would i have to get another new cable up on my roof? Also, I have Broadband and landline, do both of these come into the house on the same cable?
Virgin Media uses its own cabling. All other providers use Openreach's cabling. (Openreach is wholly owned by BT but it has to operate entirely independently, in order to ensure that it doesn't offer BT access to its cables at more favourable rates than it does to BT's competitors).
The 'old' cable in your home must be one owned by Openreach, through which you can get both telephone and broadband services from any company, apart from Virgin Media.