What’s the software that’s used in Grand Designs to show the prospective house build? No real interest other than it looks pretty swanky!

Is the fly around bit created after the house is built in real life so they can get accurate detailing?

One of my old school buddies (architect by trade) has spent a vast amount of his free time working on the following project which I am guessing is the type of thing you are thinking of

http://suplugins.com/podium/v2-features-page.php

A bit of googling seems to show that the software can do things like this

[video src="http://suplugins.com/videos/house-by-the-sea-850.mp4" /]

which is similar to the Grand designs stuff

One of my closest friends business is producing videos like the GD ones, but much better!

http://www.sourcevisualisation.com

The amount of computing power needed to do his sort of construction/fly through videos is a little mental though. Put it this way his office does not need heating even in the depths of winter.