The time line (as with all cases) is fascinating but "it is reported" is surely a red flag. For example, I would hope that undercover cops have more skills rather than parking outside the suspects house. It could have been two workman having a break for all we know. "Evidence" from "nosy neighbours via the media has a huge question mark over it.
The size of area searched would perhaps indicate cell site analys and this confirms my point I made earlier. If he visited the area of disposal with a tracable plate and/or a tracable mobile phone turned on, with his background knowledge, he knew he would be caught and relatively quickly.
Its a cliche but perhaps part of him wanted to be caught. It's early days but horrific to think of the same situation with false plates and phone turned off.
PS Geordie, I agree re extreme escalation but we should not assume he planned a murder when leaving work. He could have lured her into the car on the spur of the moment with further indecent exposure planned but she "fought him off" and he panicked.