Did you raise a ticket to our support team abut this? If so, have you received a response yet?
As long as there's webspace on your new active Plusnet account you should be able to move this over yourself.
It would need manually moving. You'd have to download a copy of the site and then re-upload it to an area of webspace on the new account. Please note that the URL for accessing the website etc. would change.
If you don't have webspace with your new Plusnet account then unfortunately it wouldn't be possible to move it over.
Hope this helps!