Someone upthread was asking about space saving Japanese solutions, but to be honest, I think everyone here tends to use those collapsible IKEA bags and doesn't sort laundry much at all. I separate a few things for handwashing, but everything else goes in one wash. Maybe because we wash everything on cold water here, so it's kind of OK for everything to be washed together?
The space saving Japanese laundry thing which everyone in the UK OUGHT to have (if only UK home building firms would build the things) is the yokushitsu kansoki (bathroom drying system).
This is where the bathroom is built as a walk-in wetroom, with a door that shuts tight with a snap, and a heat/ventilation system built into the ceiling. You hang your laundry on those portable rack things, and if it looks like rain, you carry them into the bathroom, hang them on the rails that are over the bathtub, shut the bathroom door, and switch on the heat/dry function using a switch on the outside of the door. This sends heat into the bathroom and extracts the moisture via the ventilation system, so your clothes are just gently steamed dry as they hang there. It uses little energy compared to a dryer and takes up no space, as it's just multipurposing the bathroom you have already. The clothes also don't need ironing.
Sorry to bang on about it, but it is the BEST system, and with UK homes so small these days like in Japan, there is a desperate need for space saving systems that dry clothes efficiently and cheaply. Last time I stayed with a flat-dwelling friend in the UK, her home was constantly covered in damp laundry and she was worried about moisture building up in the flat (condensation, mould). It was really hard!