Really sorry to hear about the Landy, I hope it is found and comes back..but like you I think this is unlikely.
One thing I would add, you can rule out the Cable and Wireless guys, I am about to start working for them as I move to Wiltshire next month, the security checks they constantly do and at the time of your appointment makes the C&W guys being involved rather unlikely...not impossible..but unlikely.
I only mention it because it was the only change in 'routine' that week that involved the Landy. They would have been contractors I suspect mostly digging tranches for cabling.
But as I said in a previous post - no good pointing fingers without any facts.
Good luck with the job!