Re: Not great
@Tom_
I suspect that when you move back to BT you'll still get about 12Mbps. It's likely that your connection speed has declined over the years due to contention, crosstalk, or simple increase in BB customers.
The PN community forum regularly features people either planning to move from PN due to speed issues, or recently arrived from another ISP for the same reason, and in all cases I can remember the speeds were the same for them.
I signed up for the FTTC service in 2013 and was getting 72Mbps, probably because the Exchange had just been fibre-enabled and I was among the first. Now 2 years later I'm getting between 55Mbps and 60Mbps, almost certainly down to crosstalk etc.