Thanks so much
@Jinjin after several attempts to bypass the MM chatbot I eventually got through to MM human. Annoyingly the chatbot is set up with limited options to choose and only at a one point do they let you type anything in!
Anyway they tried to help me get my password reset unsuccessfully (suggested all the same stuff as here on cache etc) and they couldn't push through the saved quote so I asked that they extend my trade in date on my original order placed on 29/8 and they agreed to extend by 7 days. I think only because I couldn't get into my account but this is the best result because that is the order I applied the UPGRADE22 code to so am back up to £585 trade in price (all things going well at inspection). Phew!
I photographed the chat screen on the 7 days extension for proof!