So the GSV view clearly shows the two bays, which makes me read your narrative as "As it was Sunday after 18.30, I thought I'd chance my arm and hope no CEOs came along. " Correct ? London councils get so much money from parking penalties they patrol the streets 24x7 and indeed, the money really does roll in !
Looking in GSV at the loading bay, there is no sign for it in 2023, one has to go back to July 2022 to see one. GSV has a later 2022 view with the sign gone.
2022
https://maps.app.goo.gl/juKNenU1RZBQAeYWA 2023
https://maps.app.goo.gl/uvduarLjdPxxW2Ss6I therefore suggest that you submit reps based on there being no sign for the loading bay, so you assumed loading was permitted in the whole bay and parked accordingly. However, wait a bit to see what the others say, as I might not be right with this argument.