I am willing to go to court for this as the restriction is ridiculous and the signage even worse.
There is no "court", but you can take them to London Tribunals. The restriction may be ridiculous to you, but will be within a Traffic Regulation Order, so saying it is ridiculous will not win any appeal. However the council have a duty under LATOR Regulation 8 to place adequate signage to indicate the restriction.
Note that the signage is not "tiny", but quite large, and there are normally two of them one each side of the restriction. For access off this very busy road, the council should have placed an advance warning sign on the main road, so is there one there ?
The video shows you charging in at quite a pace so it seems clear you didn't notice the signs, that are commonly called "Flying motorbike " signs, because there is a diagram of a motorbike above that for a car. It seems to me that this is what caught you out: -
Turned left off a 40mph Busy A road which ive used for years
Anyway, if you can confirm whether there is any advance warning sign, please, as GSV is not sufficiently up-to-date it seems.