The significance of SJL's car being sighted as early as 12.40 is that if this is true, her car must have gone straight to Stevenage Road, whether driven by her or someone else. If so, this debunks the HR sighting at 37SR of a woman whom the police decided was SJL. If SJL was at 37SR at 1pm, her car can't have been left 1.3 miles away ten minutes previously. WJ's timing lined checkably up with the time she said she was at the bank so there seems no room for error about when she saw the car she saw. The room for error is if it was the same car then as the police found at 10pm.
The schoolboy's subsequently-reported sighting of the car at 12 noon thus has to be thought about carefully. If this sighting is accurate, then the car WJ saw was there much sooner than WJ noticed it, and cannot have been SJL's. We know this because before SJL left, she asked a colleague where her car was parked. If her car had been borrowed for a viewing and was still a mile away, this question would have been met with silence, because the borrower would still be out of the office - with her car.
Hence the schoolboy and WJ sightings are most likely of a similar car in the same place. That's if the schoolboy sighting is even real. I can't think why he'd notice such an unremarkable car. It seems likelier that he just wanted to get involved in the investigation and perhaps have his picture in the paper.
This then allows the BW sighting to be accurate. She could have seen SJL in her car at 2.30 in the FPR because it had not been outside 123SR for 2 hours at that point.
If you take those three 'placings' of SJL - outside 37SR, outside 123SR, and in the FPR - they can't all be right. In fact, no more than two of them can be. 37SR and BW could both be right. But WJ and 37SR can't both be right, nor can WJ and BW be.
It is thus very odd that the police dismissed BW, whose sighting was consistent with a supposed abduction from 37SR at 1pm, yet accepted WJ, whose sighting emphatically wasn't. Alongside speculatively deciding that SJL was the woman seen outside 37SR, the police also accepted an account from WJ that proved SJL could not have been that woman.