You used to be able to buy units like this in NZ. I bought one about 12 years ago with Delonghi branding, quick-fit adapters and pre-charged with refrigerant. Cost about $1000. Took about an hour to install. It lasted about 10 years, and worked "okay" over that time.
Lower COP than quality units, and placement is limited due to the length of hose. As I understand it, they were taken off the market in NZ/Aus because the power to the external unit was supplied via the indoor unit (which plugged in to a standard wall outlet), there was no power isolation switch for the fixed wiring to the outdoor unit and so they didn't meet regs.
Apparently they do seem to meet UK regs:
The problem is that such systems often tell you to remove the air from the connecting pipes by deliberately releasing refrigerant into the environment. So definitely not allowed.