Ok - clearly Nothern Rock went under, so any new company is not necessarily bound by the terms.
But what I would do is this:
1) write and make a formal complaint. They will investigate the matter and report back to you.
If they do not uphold the complaint you can then go to next step
2) go to the Financial Ombudsman. They offer a free, independent service and can investigate your complaint for free.
They can be found at: www.financial-ombudsman.org.uk
That may resolve the problem for you.
Can I clarify anything for you about this today, please?
If not, I would appreciate a 5-star rating for my answer, by clicking the button at the top of the screen. If you need anything further I am available for a follow up at no extra cost.