>>Are they about to fold??????>>
What a ridiculous observation.
I know PlusNet has had some embarrassing moments lately but The Register, which would be amongst the first to post any thing amiss, last did a story on the company on July 20th.
Your remark that "I'm told they are being inundated with complaints" is most likely due to the loss of some subscribers' e-mails last month.
Not the happiest time for it but it's not the first ISP to suffer from such an incident.