AIUI, DV's thinking is that the time sequence for the diary retrieval looked roughly like this:
9.30ish - calls start between PoW, bank and SJL re lost property
11ish - arrangement made to fetch stuff after work
12ish - KP turns up, goes off for lunch with MG.
12 to 12.30ish - punter calls in wanting a second viewing of 43 Waldemar. Second viewings are buying signals, so this takes precedence. Catch is, punter can only come after work. SJL books 6pm viewing.
12.30 - SJL realises she now can't go to the PoW after work because she has a viewing, then tennis. She's busy till 10, so she calls the pub and asks to come now.
12.35ish She realises she needs to justify not being in the office if KP and MG return, so she fills in the first property address she can think of and the name she associates with it.
12.40 she heads off to the PoW.
Next day: CV tells police SJL was expected that evening and never came.
1 year later: CV has now seen the diary and the 6pm appointment in the papers, realises SJL would never have said 6pm, and changes his story to suggest others besides himself knew she was heading to the PoW.
If DV's right that MG had already gone to lunch when SJL left the office then MG can't have remembered her collecting the keys. I am not really sure how important this detail is to his she-didn't-take-the-keys thesis though. Whether she took the keys or not, the absence of any evidence she was ever inside 37SR undermines HR's claim to have heard the door as someone came out.
What's a bit more troublesome is that the cancellation of the evening PoW pickup relies on DL's account of a tennis date being accurate, and on the assumption that she couldn't possibly have gone at 9pm rather than at 6pm.
DL certainly later manipulated the picture to quash any suggestion SJL had ever been sexually active. Interestingly, she was not anything like as bothered by the idea that SJL might have been doing something financially shady. She took months to disclose the final Sunday conversation with SJL - which was about dodgy property dealings - apparently thinking it not important. IIRC DL even suggested SJL might have got involved in somebody's mortgage fraud - almost as a sort of "acceptable" thing you might do that would get you killed.
Whether DL was already doing this by Wednesday 30th July is less clear. It's also not clear that SJL couldn't just go to the PoW a bit later, given it was close to home.