I think I’ve settled on a compact camera, connected to a laptop (we have a spare one in the office) that is loaded with GBTimelapse software. I’m looking at a SH Canon G10, which you can get a mains adapter for.
It’s going to be indoors, looking down from a window opposite the site so the weather ingress isn’t a problem. Plus, the camera can be used as a general site photo camera when not being used for the timelapse.
As the site will be quiet during the weekends, the software will allow me to programme it to only operate at certain times and on certain days.