The IP address allocated to me keeps getting blacklisted so I suspect someone sharing this is sending out spam. Virgin do not seem to be able to provide an answer and this can affect the delivery of email.
The only people "sharing" your IP are the people connected to your hub, IP addresses on the internet are, by requirement, unique and only one "location" can be using that public IP at any one time, so if something is blacklisting you its not because someone else is sharing your IP
It is in the nature of this Forum that people who come here think that the most dreadful things are going on with their security and that VM are always to blame. Neither is true.
First of all, the IP address that you are assigned by VM is almost bound to be blacklisted on Spamhaus and SORBS (see ravenstar68's FAQ which you have been pointed to above) because they blacklist IP addresses which should not be running mail servers of their own. That means your IP address at home given to you by VM. Never checked when you send mail. Nothing to do with the mail system checking that does go on. So that blacklisting makes not a blind bit of difference to the e-mail system world-wide because the checks that the e-mail system runs on IP addresses to make sure that they are clean of spam are checks on the IP addresses of the mail servers themselves (ie the mail servers run by the ISPS or ESPs). That has nothing to do with you. You can't see it and you can't change it, if inadvertently, those mail servers get blacklisted for sending spam as they sometimes do.
If someone else appears to be sending spam using your e-mail credentials then that is not VM's fault. It is because somehow your credentials - username and password (particularly the password) have got into the hands of hijackers.
You can sort this easily and simply by following this guidance to the letter: