Sorry to say it, but I don't think you don't have a particularly strong case, I'm afraid. The bus stop is approximately 50 metres long so longer than the one in the London Tribunals case you have posted. However, it has the necessary sign located approximately in the middle of the stop :-
https://maps.app.goo.gl/X5kzfvkPWaomGbFG7Of course you could argue that two signs are necessary as the single one cannot be clearly seen if one stops at the start of the bus lane like you did
In addition, there is the broad yellow line which should have alerted you. You could have stopped on the double-yellow lines either side of the bus stop as boarding or alighting passengers is an exemption to them, but not for a controlled bus lane like this. Virtually all bus stops like this in London are now controlled and enforced by CCTV
Of course you can try your luck at London Tribunals with the full PCN penalty in play; it is your legal right, but first you must submit reps to the council. You could cite the case you have posted, pointing out the bus stop is longer than the one at London Tribunals, yet has only a single sign, and that there should be a sign at the start of the bus lane.
