When the cistern on my toilet is filling it makes a right racket. Do I just need to change the float valve or could it be something else?

Albert Ball cock?

take it off the treadmill

Try closing the main stopcock while the cistern is filling and stopping when the noise sounds bearable. Then check that sink and basin taps around the house are still delivering enough flow.

Slightly closed the feed valve to the cistern. It still made a bloody racket. :-/

If you’re feeling flush, why not splash out on a new one?

Take a pic. More than likely just a rubber needing replacing. Flush toilet and open the basin cold tap and see if the noise stop/lessens.

get one of these

More than likely the fill valve has got a bit of dirt in it. Note down what it looks like, what type of float arrangement and if its side or bottom entry… Yup, I can’t help sniggering too 😉

Then, go and buy a new one and replace.

Why replace an entire float valve when it could be a 5 min fix costing 50p?

Because when you know what you’re doing, it’s a 5min fix.

When you don’t know what you’re doing, which I am having a punt on the OP isn’t too familiar with, due to the nature of the question, it can be much longer trying to figure it out, not figuring it out and then going off to buy a new one because the old brittle plastic parts have snapped off trying to twist against the limescale seal that has formed.

Trying to cut out the middle man I suppose.

Maybe not the “teach a man to fish” approach, but rather ridiculously now, I wanted to keep my suggestion brief and quite why I’m even bothering to defend myself is also puzzling me. But there you go 😕

And yet you assume the OP has the skills to replace a float valve 😉

Haha! Touché! 🙂

Ours did that. I think it’s grit in the supply bit (technical term). I held my finger over the end where the water comes out to increase water velocity (like on end of a hose pipe). Did that a few times and it hasn’t happened since!

I shall finger the rim and see of any dirt comes out before messing with my ball (singular) and cock.