Agree (and welcome to the discussion BTW). However, as DV points out, you really would think someone would have asked MG and colleague how they had got into the property to look for SJL if she really had gone there taking the keys. There is not a single contemporary mention of there being multiple sets, it wasn't normal practice to have more than one, and if there were still a set in the office, who was it who asserted that this was the extra set out of two that they had for that property? Who swore to that off the top of their head?
The next problem is that HR did not say he saw SJL; he said he saw a blonde and a man who was about 5'8" or 9" emerging from the house. It was the police who said this was SJL. How were they emerging if she didn't have the keys? If she did, well, did she leave any prints? The perp could have walked around not touching anything, but someone had to open doors, and if it wasn't him, it was her. Yet we never hear that there was fingerprint evidence proving a visit by her. If there are no prints then she was never inside, which means HR cannot have seen her emerging.
The other witness usually cited, ND, said he saw a couple but it could have been 4pm. HR identified a 44-year-old Belgian as Mr Kipper. Taken together it looks IMO like HR has no idea what he saw or when he saw it, and that ND probably saw the search party, MG and colleague, not SJL herself.
Another strike against the involvement of the 5'8" man supposedly seen outside is that the Fiesta's seat was found pushed all the way back. A man of that height would not need to do this IMO. If he did, then given that this is the average male height, it would mean that 50% of males would find the front seat of a Fiesta cramped. From what I recall of small cars, the front seats fit anyone and it's the occasional seats in the back where space is saved. So the driver of the car probably wasn't anyone of the height of the man supposedly seen outside 37SR.
Cannan was never put on an ID parade and the case against him (that the CPS does not buy) consists of insinuation and perfect recall decades after the fact. The only bit of "evidence" that he was involved is the opinion of some police officers that one of the artists' sketches looks like him.