Nice work
Have to admit to not having really looked into this properly before, but now that I do... the only thing running from external to internal unit is hoses carrying refrigerant back and forth right? (and power presumably for the external unit)? In my head for some reason I'd always imagined there was ducting carrying air to the outside (but now that I think about it I can see that makes no sense!)...
I was kind of hoping maybe I could get an external unit that splits to multiple indoor ones and maybe put one on the top floor landing (3 storey town-house) and one in the hallway, and that somehow between them they'd condition air up the centre of the house that would spill into the other rooms (maybe I wouldn't get ice-cold temperatures everywhere but it'd be a lot cooler than it currently is)... but as I read up on it more that seems like it wouldn't work at all... then if I try to think of a single room or even a pair of rooms I'd want to be conditioned it's really hard to choose which!!!