I'm a bit confused. Did your communication with TFL solely request the video and not include anything which could be construed as representations against the contravention?
You legally have until 28 July to submit representations so if you haven't submitted any yet, they shouldn't be limiting your opportunity to only 14 days from their letter.
Subject to confirming no representations submitted yet, I would sit tight for a couple more days and see if the video comes. Are you able to submit representations electronically or only by post?