Here you go, I've worded it on the assumption that you'll send this on 11 June as that puts you just over the six month mark:
Dear Transport for London,
This is not a complaint about the merits of PCN GX19906586 and I am not asking as part of this complaint that the PCN is cancelled. Instead this is a complaint about the inordinate delay in my representations being dealt with, my representations were received by you on 10 December 2024 and over six months have now passed, and there has still been no reply.
While I appreciate there is a statutory process that must be followed, I am entitled to that statutory process taking place within a reasonable amount of time. My case is not unusual or complex and there is simply no justification for this inordinate delay.
Please would you issue a response to my representations as soon as possible and in any event by the end of the month.
Yours faithfully,
If they're stupid enough to issue a notice of rejection, it'll be open and shut at the tribunal as it's way over the three month limit that the tribunal normally applies.