You can try the pre-installation and delivery team on 0800 052 1734 and see if they can tell you anything helpful ref cable installation. Don't place any great faith in what they tell you though. Any date they tell you simply comes from reading off the screen in front of them and there is no guarantee it is an accurate bit of information. Much of the cable installation work is sub-contracted and, based on many past topics on here, VM seems to have little/no control on how/when it happens. It seems to rest heavily with the contractor. Often they just turn up.
VM does not usually expect anyone to be in for the external work. The contractors will typically install in a way that is easiest and quickest for them.
If you want the box installed in a specific way/location you'll need to either get an idea of the cable date from VM and make sure someone is in to supervise what the installer does (the best option if possible) or you will need to leave some very clear indications (written notice outside etc.) of where you want the box to go (which may well just be ignored by the installer if no one is at home).