ball cock

Hi all! Just a quick one, my toilet cistern has a leak from the water inlet valve into the ballcock (picture attached). Is it the ballcock I would need to replace, the valve or both? Many thanks in advance for your help.

Next topic! I'm getting on with stuff today. :) Toilet flush: The cistern never really gets full and the valve never fully switches off. I've poked around and it seems that the bit that the ball float pushes into to stop the cistern filling is sticking. What's that called? Inlet valve...

Ladies and Gents, My house, it seems, is slightly non-standard. I need to replace the float valve in my cold water storage tank, but of course it doesn't seem to have a standard 15mm fitting. I believe it to be 20mm, like the mains water stopcock fitting, which is "actually" a thread diameter...