The only remaining issue I can see is the shortfall from 7/7/19 to 29/7/19. As the Tribunal has confirmed there is no error and their decision remains unaltered, I assume the DWP will issue back pay for that period after receiving their copy of the Tribunal's reply.
I have received another award letter from the DWP with the original start date of 8/7/19 as determined by the tribunal. I also have received a one off payment that covers the shortfall.