Hi , if you have time I’d be really grateful if someone can answer this question so I know what to buy and what to ask a local tradesman to price for . Have a bath / shower mixer valve which is Grohe , it must be 10 years old , they are a great company to deal with and have sent me a new grub screw which I though would stop the wobble on the handle ( see vid ) but I can’t get it fixed in place as i guess it’s just old now . Don’t care about the wobbly handle but when you run a bath the water runs cold . We have an oil combi ( pic attached ) but the kitchen tap & basin tap in bathroom seem to run hot ok . So my question is , do you think it’s the shower valve that needs replacing / and the wobbly handle that is doing it or the valve is just knackered - thank you