I included the GSV image in the original post with a red marking of roughly where I entered and then off to the left, also GSV link is in the post, let me know if you aren't seeing those for some reason?
Sorry, missed that ! So I went into GSV satellite view as the street views are out-of-date, and seeing the white manhole cover and looking at your red line in the GSV view, I reckon you were just under 30 metres in the bus lane. I don't think an adjudicator would consider this as de minimis, especially as you undertake a couple of car in doing so.
So unless a 'technical' appeal is suggested, I don't think it worth taking to the Traffic Penalty Tribunal. Sorry if this isn't what you wanted to hear, but it's best to be honest with these things. Others may disagree with me, so wait a bit to see in anyone else comments, but don't miss the deadline to pay or submit representations.