I agree with what posters on this thread have been saying recently.
I think that whatever happened at the Travelodge a couple of weeks earlier was the crux of the matter, I think that Mr X told Leah it was over between the two of them.
The TVP said that Leah had seemed stressed at work just before she went missing, and I think this break-up was the cause of her stress.
We know she went out the evening before she went missing between 6.00 - 7.15 pm, I reckon this was to either meet up with Mr X somewhere (car park at Premier Inn maybe), or found somewhere quiet out of the house where she could phone him (so her parents couldn't hear the conversation at home).
Two likely scenarios are that either Leah had learnt about Mr X's upcoming arranged marriage and had threatened to blow the gaff on him, to his future wife, his family, work colleagues, etc. Or that possibly she was pregnant, and again had said she would tell everybody - possibly the following day.
This would of left very little time for Mr X to do anything about it, so he had to resort to drastic action.
The following morning Leah was, to all intents and purposes, on her way to work as usual. She recieved a message on her phone to say 'meet in Premier Inn car park' or something like that. When she got there not Mr X but someone she knew, a friend of his, maybe even a taxi driver she knew, told her to get in. Trusting them she did, then was spirited away.
Leah left her home around 8.00 that morning, was seen on CCTV at Buzzacott Lane at 8.15, witness sighting at TeleTubby Hill at 8.20. From there it takes 14 minutes to walk to the car park at the Premier Inn, which would place the time at 8.34.
8.34 was exactly the time her phone was switched off.
All MOO.