Bought in 2020, removed and thoroughly cleaned, this is a bidet attachment that fits under a normal toilet seat and attaches to the cold fill pipe of the toilet cistern with a TV piece.
It's in good condition (a couple of spots of rust from the bolts on our old toilet seat and a little limescale) and you can probably fit it yourself if you're good at DIY. I may be able to find the fitting instructions but it's like any other cold fill bidet seat.
Collect from close to East Putney tube station most days and evenings