In my experience of observing my own and neighbours installations the engineers are usually very flexible in meeting your requirements but you have to be there and watch everything like a hawk to make sure they do a good job or they will take shortcuts e.g. make sure they silicon gun any holes in the wall. One thing they won't do is high ladder work ... VM supposedly has some specialist teams who can but they are as rare as hen's teeth.
Thanks, that's reassuring. Our house frontage is quite wide, and depending on where the street connection is, the engineer may have to install quite a long run of cabling outside before bringing it into the house. No ladders should be needed though!