To be fair, the council camera is positioned some distance along the bus lane, not at its start. There is a clear Bus Lane sign, (two in fact), yet you carried on in the bus lane for the whole distance seen in the video.
So whilst I agree, there should really be a sign at the right turn by the last set of traffic lights, an adjudicator could consider there to be sufficient signage. On the other hand, he could agree with you that not having and advance sign means they have not met their duties under LATOR Regulation 18, but it would not be a slam-dunk win in my opinion.