I bought a humanscale freedom task chair in a second hand office furniture suppliers. Several hundred pounds worth of office chair for a just over a hundred quid. Never been used, still had the delivery wrapping and labels on.
I got mine from this place. stock varies a lot as do prices depending upon how much they’ve got in and how quickly they need to shift it on. I think you get a better deal by visiting and poking around as it’s a real jumble sale of a shop. When I got mine I tried a couple of shabby looking chairs and wasn’t so keen and then fella mentioned that he had a virtually new one knocking about upstairs if I wanted that for the same price.