I'm astounded the builders would actually be using anything else these days.Holy smokes! I'm hoping to keep it as low as possible, which is already going to be hard enough as we want to change to LED down lights throughout the house.
A length of conduit is just an easy way of getting past the wall battens. You could just drill holes at appropriate points and leave some cord to allow the wiring to be pulled.I would very much consider this, but unsure if Brighton will be very obliging as they'll know I'm trying to skirt around their outrageous prices for HDMI cabling. It's certainly something I will be asking at the appropriate time. Only trouble I see with this idea is that I'll be pulling a cable up a wall cavity and then over a ceiling to the other side of the room. That might be a little complicated for a conduit?
To be honest, your builder sounds like a bit of a pain. I had access to my house throughout the build, and was given keys at lockup. I know that most builders aren't that helpful, but this was discussed at contract time, and I would have walked away if not agreed.
Wifi is all well and good, but at a later time you may find that items such as security cameras actually need cable connections. POE (power over ethernet) is very useful. I would rather use a couple of wired access points, than rely on any form of mesh system. Look up the Ubiquiti range (ubnt.com).
Also, ensure that your internal walls to the garage are insulated.