The deadline to make representations is Sunday and I wouldn't take any chances.
If you've not had the video in Saturday's post at the latest, send a representation as follows:
Dear Transport for London,
Despite repeated requests, I have not received the video. As I have not seen any footage, I can deny that the contravention occurred and I request that if you reject this representation, you send me a copy of the video footage you rely on. I trust that given the delay in sending me the video, you will reoffer the 50% discount in any event.
Yours faithfully,
Also please give us the number plate so that we can see the case history on TFL's website.