Well. Our plans for a ducted loft system to three bedrooms seems to have gone for a burton.
Our fitter has done some more research on what would be needed, and reckons larger units to make up for the heat in the loft, inlet and outlet vents to each room, and a separate unit for each bedroom would be required to do the job properly. Resulting in a much higher price that we'd originally planned for - £4,500 for just the parts, and probably 5 days of labour.
Three wall units (fed from a single outside unit) would half the cost.
There were two main reasons for avoiding wall mounted - the aethetics, and the worry about needing a condensate pump and the noise that would add. Neither of the bedrooms has a suitable outside wall for mounting the unit, so the condensate pipe would have to go up from the unit and along the top of the wall to outside.
But to half the overall cost, maybe we can deal with both those issues!
The other option is ceiling cassettes. So he's going to look into them too. I presume that would still leave them needing a pump for the condensate though. And I think they also are going to be less efficient like the ducted system, because the body of the unit is in the hot loft.
