Opella Cistern Bottom Entry Filling Valve Adjustable Arm 1/2" with Ball Float
Range from the cheapest replacement of a toilet float valve £40 (East London Gas based in E3) to the dearest replacement of a float valve £100 (Boiler Repairs London based in E9).
Comparing plumbers estimates for replacing a toilet float valve in the cistern tank gives you an idea of who will be better value but the best way to compare costs is to get actual quotes.
What to do - Get rates and quotes to replace a toilet float valve in Broadgate by posting a job with HaMuch and we will send it to plumbers in Broadgate.

"Replace float valve in toilet cistern"
LONDON
"Replace float valve in toilet cistern as well as the other parts in the water tank. Rubber gasket (80mm) is old with limescale and disallows water from filling the tank."
SE1