Well, it's the normal NtO, but do be aware that you must not ignore it, or it's game over.
However, advice is DO NOT PAY IT, but submit a formal representation based on your informal challenge. Newham know they are in the wrong so act on the fringe of legality by rejecting your reps which are valid in law. They do this because this is 90% a money-making game, and they know if they reject, then >95% of people then cough-up. If they reject your formal representations, they will in all likelihood, re-offer the discount, to, again, get the money in.
So basically, it is all about whether you are prepared to stand your ground or not; it's that simple.
