Hi K,
Thanks for that. I’ve run a pipe brush, and also a piece of garden wire, down the drain as far as they will go. Both items hit something solid after 60 or 70 cm and will go no further. Is it possible there is a right angle in the drain, or should it run straight-ish all the? i.e. should I be able to run a wire all the way down and out the bottom?
Is it worth trying to get some drain-unblocker fluid or similar down there to see if that helps?
Thanks,
Pete.