Parking within the limits of a pedestrian crossing is generally a big no-no. Even just stopping a motor vehicle is not normally allowed (apart from the obvious to let pedestrians cross, prevent an accident etc.) The OP seems unlucky to have been caught but I wouldn’t risk it. Being caught on a red route in that London was bad enough but I wouldn’t risk points on my licence, I bet they’d really love that up there.
A “public service vehicle” is allowed to stop on the far side of a crossing to board or alight passengers (this is basically a bus operating a local service in this example, AIUI, i.e. not a coach or taxi). I’d like to know the reasons why this is allowed, perhaps interested parties influenced this outcome in the dim and distant.
For further reading q.v. legislation.gov.uk/uksi/199 … on/22/made