Or, the other reason people sometimes don't mention the name of the person they are seeing, is if they are having an affair.
As a PP said, the keys could have been put back by force of habit, if they had been taken by someone that SL was working with. Or, there could have been two sets of keys, but someone she worked with has a vested interest in saying there was only one set.
If SL went to meet Mr Kipper at 12.45, then found a colleague already there when she arrived, who had perhaps duped her into the viewing as a means to getting her alone, that could certainly cause an argument. London was awash with Champagne at that point - it wouldn't be too much of a coincidence for a suitor she worked with to have tried to meet her at the property, hoping for a liaison with Champagne.
As I am totally flying by the seat of my pants with this, I have no idea where the cars fit in, except that lots of people at that time had black BMWs if they were high earners.
It seems clear to me that sightings of SL driving erratically, if accurate, were POSSIBLY a way of attracting attention to herself in the eyes of the public. Particularly if she was staring at passing motorists, willing them to know she was in trouble. However, this makes me think that whomever she was with was not threatening her with a weapon - who would risk being attacked whilst driving by purposefully driving erratically?
There is another reason that any similar incidents may have stopped when Canaan was jailed: whoever had carried out similar crimes would have known that they had a golden opportunity to pin them on someone else.
The motor racing and champagne are, I feel, red herrings, as is the date always leaving early. Lots of people enjoy motor racing but, like buying champagne, it costs to do so. Was JC in a position to be able to pay for this stuff? His wages as a porter would have been low, and can one be approved for credit when the address given is a bail hostel?
The leaving early also could point to an affair - SL reportedly made comments that she suspected the man she was seeing was married. Well, that is an awful lot more probable than someone being on a bail curfew. And was perhaps a way of 'admitting yet not' that she was having a relationship with a married man.
Also, if the man kept leaving mid date, why would she have kept meeting with him unless he had been able to sweet talk her between dates? Which would fit perfectly with someone she worked with giving her a cock and bull story the next day to keep her sweet. It isn't as if one could send a lengthy text or email in 1986. It would have had to be by phone. Phone calls from a bail hostel would have been from a public-type pay phone. As would calling from a payphone. I doubt JC would have had a landline in a bail hostel. So if he always used payphone, which she will have known from the "clunk" when the money went in when she answered and the "pips" at the end of the call, then JC is unlikely to have had the chance for lengthy cock and bull stories explaining to SL why he left. Wealthy businessmen from the West Country wouldn't have wanted to be seen dead using a call box. So how could JC have talked her round between meetings without blowing his own self image of his persona by using a call box? I know that's tenuous but it doesn't make sense to me.
Also, why did SL's employer start calling people concerned as to her whereabouts, when there was a later appointment in her diary. Surely it is more logical to assume that she had been delayed between appointments, but had forgotten to take the keys for the second viewing with her, or that she would pop back for them? Especially with her bag being left in the office? It would be more logical to assume that she would be coming back. One would surely wait until after that appointment time before phoning parents etc to check up on SL. Unless someone she worked with knew she wouldn't be coming back and wanted to cover their tracks rapidly.
Whilst there is most likelihood of JC having been involved, I do think that discrepancies and other possibilities have been overlooked. Interesting that I think I read that her boss was out of the office at the time.