Just do the appeal as advised!
They will cancel, and with great impudence, tell you not to be such a naughty person in future and that you should always obey their rules.
If it were me, I simply respond to their cancellation notice, telling them to refer to the answer given in Arkell v Pressdram (1971).
I haven't paid a single drop off fee at Heathrow, Gatwick or Luton for years.