This is a widespread scam and not targeting old Pipex customers specifically
The lists of email and passwords appear to be fairly old
I agree with you there; in all probability anyone with an email address will eventually receive a similar email. Judgements are clouded with apparent consequences if action is not taken immediately and far from a few being taken in, there are probably thousands paying up. Then there is the shame factor coming into play by not seeking advice from a friend because you don't wish to admit that porn has been viewed.
If you have a nagging feeling that you need to research this matter with Google, what exactly would a novice user use a search term that would bring up a definitive response that doesn't set off a knee jerk response which in the majority of cases is completely unnecessary?
IMHO opinion the following is worth adhering to:
NOT to pay out anything;
In no circumstance NOT to respond to the (blackmail) email;
Ensure your router and connected devices are fully patched;
Switch to an anti-virus product that has a good reputation that does what it says on the tin;
Deep scan the computer to remove nasties that WILL be found. To do this you may need to seek a source/organisation that will do the task for you. DIY tools are not good enough!
Start to break away from using ISP provided email address(es).
Use a password generator to create strong passwords.
Feel free to add to this listing