Bear in mind that:
(a) the pre-install survey tech may not be the herbert that eventually turns up to do the job
(b) chances of the survey tech communicating with the installer are low
(c) quality of some installs is less than optimal.
Which means today you should get some useful guidance and be able to discuss what you'd like, but you'll need to be in and explain it all again to the actual installer, who will probably have a ridiculously short window to complete the job. A further consideration is that VM's record on new connections is hugely variable - some are on time, some are massively delayed for no obvious reason and with no explanation. So no matter how clear and simple it all seems, no matter what VM promise, don't cancel any existing provider until the VM connection is in and working.