If you have past the end of your contract then you should not have to pay the cessation charge.
Your contract, (i.e. your minimum term), expired or not is nothing to do with the cease fee. It is to do with complete cessation of broadband on the line.
The fact you were not charged a cease fee is surprising, but you may only have given us half the facts. It is very confusing when you say "able to leave (not migrate in anyway)", as that makes it very hard to work out what process was actually gone through on your line. You could only have either migrated away from Plusnet or ceased the broadband.
It's possible that with the current chaos in Plusnet admin systems the lack of a charge is a simple mistake in your favour. (A very rare occurrence LOL).
It's also possible that your move, if ordered later than June 20 2015, was a simple migration. Was your line rental also with Plusnet?
The indispensable man or woman passes from the scene, and what happens next is more or less the same thing as was happening before.
My broadband basic info/help site -
www.robertos.me.uk. Domains, site and mail hosting -
Tsohost.
Connection - AAISP Home::1 80/20. Sync 59999/14372kbps @ 600m. -
BQM