The shower spray valve in the bidet needed replacing because hardly any water was coming out and I knew it would be a struggle because I had already replaced the hot and cold valves last year. I say a struggle because over the years the water reacts with the metal and things get stuck. For example, the chrome tap that you turn is screwed to the top of the valve with a brass screw which has a tiny slot at the top, as opposed to a crossed Philips. Anyway, this one was impossible to remove, especially since the slot gets destroyed after too many attempts. In the end I had to drill the top off the brass screw in order to remove the chrome tap handle, otherwise you can't get to the valve and it's an odd looking valve which fortunately I managed to buy in the local plumbing shop for $23k cash.
Putting it all back together was simple and I used PTFE tape around the valve thread, cleaned all the joints with a drop of oil and put a tiny bit of oil around the thread of the new brass screw.
Works like a charm now and a satisfying job to do.