'illegal' in that manufacturers add on a usb port and the basic board to tick the reusable check box.

I'm still seeing almost as many of these cast on the streets as I did a year ago.

All of the disposables I've seen have USB ports for charging because they come with more juice than battery power sufficient to vape it all. You will have to recharge multiple times for one disposable. I'm not in the UK, but I have seen something of a shift to separating the battery component from the vape tank such that you can just buy a new disposable tank and reuse the batteries. Maybe something like that might work in the UK grey areas.