I'd say probably no, but not in a way that would get you out of your contract. I can think of a few reasons why you wouldn't be able to get the full speed, and all but 2 of them wouldn't be Plusnet/Openreach related.
The two that might would be down to either equipment on the Openreach network that isn't working well or the equipment hitting their capacity. Both of these Openreach should be able to resolve.
The rest of the many reasons would be down to your setup and equipment. For example, I can only hit about 300Mb on my FF900 from my very high spec work laptop, but can from my much lower powered, and fairly old personal laptop. The reason being, my work laptop proxies all traffic through other services, which limit the speed quite a bit.
Someone else has replied whilst I've been typing this, and the speed profile could be set incorrectly in the Openreach systems, though that should be easier enough for them to check. It's not something I've heard happen before, but its possible with a relatively low number of people on the technology that it's currently a rare occurrence.
Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.
