I don't think he'd planned on, bargained for or was relying on anything

in his defence - I don't think he's a master criminal or a long time fantasist murderer - I think something hit the fan that morning and he left evidence everywhere! His car was allegedly seen parked up near where she was found, which of all the places and things he could've done with her, especially if it had been planned, she could've been missing for ... well, Forever. But instead, he left her close to home in a fairly busy spot and I've not heard of any 'shallow grave' so easy to find ... either he had some conscience and wanted her to be found or he really just panicked and didn't have a clue what he was doing?
Yes, I tend to agree with this. I also don't feel he is some kind of master criminal and I think whatever happened was not planned at all.
My initial thoughts were that Paige did leave the Deli and JL chased after her, offering her a lift because he needed to talk further with her re something that had been said between them on that morning. As has been suggested already, perhaps he overstepped the mark and she threatened to say something to others.
However, on further thought, I can - just about - see that whatever happened might have taken place in the Deli. Presumably there is a back section, not visible from outside and JL and Paige could have stepped back there to * talk * and JL could have quickly locked the door of the Deli before they did so. Still took a risk that he didn't end up with customers outside, but perhaps temper or panic overcame that.
If this is what happened then I also tend to think he hid Paige's body in the Deli, locked up and went away to compose himself, clean up and also perhaps to pick up something else - holdall ? - to put Paige's body into.
I am guessing that someone else comes in to help at the Deli from 10am as he does ( or did ) takeaway deliveries from that time, so he needed to be back before then. Hence his return about 9.30am.
Then I think he had no chance to move Paige's body on the Saturday or Sunday. He closes at 3pm both days, still daylight, and even if he drove somewhere with her, chances he might be seen. Not to mention, probably had family commitments over the week end and couldn't justify being away from home.
So he waited until early hours Monday morning, when he could have used the excuse of needing to go to the Cash and Carry before opening up the Deli.
So he could then move Paige out to his car, while it was still dark ( obviously didn't know about the cctv ! ) and drove out in the direction of the Cash and Carry outlets.
On the way, he leaves Paige at a spot which he probably knew was a meeting venue for young folk, and also the site of some fights. Hope being that it would be thought Paige had gone there and been caught up in some disturbance.