The real case against Cannan is probably the information against him given by the snitch Taggart. This is inconclusive because it was given years after the fact and has not led to actual evidence of any kind. That would have to have been gathered at the time.
The ostensible case for it being Cannan is largely the made-up sightings the public has been cajoled into coming up with over the last 25-odd years. This is all new information the police didn't have in 1986, so it can be argued that it's not their fault they never caught anyone, because they weren't told key stuff at the time, see?
Between no one wondering if any criminals recently released from HMP Scrubs, Wandsworth or Brixton might have anything to do with this disappearance, and the family editing the evidence to hide the fact that SJL lived like a normal 1980s 20-something rather than a virginal 1940s Methodist teetotaller, the police were left with trying to identify and place everyone last man she knew. Unless the killer was in her diary they were never going to find him.
It's not actually possible to rule Cannan out. There's nothing that says this was definitely him, but neither is there anything that says this definitely wasn't. So this leaves us with the likelihood that she went off with someone she already knew, was taken inside a house or other building to which this person has access, and was there killed out of sight. Given the FPR car sighting at 2.45 (I believe BW on this), and that the killer had control over her car in order to get rid of it by 4pm (I don't buy the WJ 12.45 sighting), this says to me she was taken somewhere between those hours and killed. This happened either then or not long after the killer returned from dumping the car.
Wherever it happened, she had to get there, be lured inside, be imprisoned or killed, and the perpetrator then had to to get her car back to 123 Stevenage. He then had to return to wherever she had been left. While she could have driven some distance in the time, logically wherever she was taken had to be reasonably close to 123 Stevenage so the killer could drive there in her car then walk, bus or cab it away inconspicuously.
So yes, within a small radius of Fulham; in fact, personally I'd narrow it down from five miles and say within 1.5 miles of 123 Stevenage. Going clockwise from bottom left, this is broadly the area from Barnes Bridge up to Chiswick and across to Hammersmith, thence via Earl's Court to Wandsworth Bridge and back across to Barnes Bridge. It takes in what is now the London Wetland Centre, which superficially looks like a place you could dump a body. But this would be tricky in daylight, the abductor would have been juggling cars if he was getting rid of SJL's car, and it's a long way on foot. Within my 1.5 miles, I'd guess the northern part and north of the river would be likeliest. The southern part is a bit more genteel and contained more intact houses; the northern bit, Hammersmith (towards where she was last seen driving) and Earl's Court, are more flats - and houses subdivided into them - with a more transient population.
Again, this fits Cannan's accomplice's address, but it fits many others too.
