Personally I would not entertain PPC's with any corrispondance other that of answering to a bonified court summonds for the following reasons:
1) They have written to you as the RK and not the driver - their first failure in their attempt to prove a contract exists.
2) None of the corrispondance they send are recorded and therefore they have no proof of delivery to show a court.
3) By responding, you only prove that you exist and simply encorages them to persue you more.
4) The game they play, is that of intimidation - no corrispondance from them is designed to correct an incorrectly issues invoice - their only agender is to extract as much money as possible form you with the least amount effort - sending threatening letters serves this purpous excellently!
5) In entering into a 'dialogue' with these types only adds to a very stressful situation - ignoring is by far an easier and less stressful option in my view.
As a last point - if I ever (
and I'm quite looking forward to it in a funny way) go to court to face a PPC - I will be delivering by hand to the PPC, in front of the Judge, a letter. It will be along the lines of the following:
By reading this letter you agree to enter into a contract with me and agree to pay me immediatly the sum of £10000 in compensation of all the stress and anguish caused by these proceeding. The sum of £10000 will allow me to take a very nice luxury
holiday
where I can relax and forget about everything your company has put me through over the last 'XX' months in alledging that a contract existed between me as the RK and the landowner and having suffered continued harrasment in your relentless persuit of monies alledgedly owed.
This I think sums up well the question of contract law that the PPC's are reliant on in winning any case in court.