I'm a bit embarrassed to admit that after all this time, I have just discovered two things quite interesting about Poynders Court.
1. There is a bus stop
directly opposite. I can't believe I hadn't clocked this, I'm sure lots of you had. Buses in London regularly stop at almost all stops (because there's almost always someone either wanting to get on or off). So, if it did stop a) it's far more likely we'd have a witness, and b) the bus camera footage would be 10-15 seconds long (or however long it takes to stop) whereas I had always assumed it was 'passing' (very short) footage. However, seeing as there aren't witnesses (we don't believe), it's just another example of SE's horrendous bad luck!?
2. OK this one I am really mortified I didn't notice before. You can go *all the way* around the back of Poynders Court on Google Street view. I don't yet have any extra theories or knowledge off the back of this, and perhaps you all already knew this (I didn't!!), but it's quite useful for getting a 'feel' for the event that the accused either a) drove the car around there and 'parked' in the turn-in 90 degrees (some people have suggested this), or b) that SE ended up running into there (hence the forensic search). Anyway, can't believe I hadn't noticed you can
Street View it, happy sleuthing.