Range from the cheapest replacement of a toilet float valve £25 (H&F based in CR4) to the dearest replacement of a float valve £85 (Emergency Plumbers 24/7 based in SM4).
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 Morden by posting a job with HaMuch and we will send it to plumbers in Morden.

"Replace float valve in toilet cistern, water keeps flowing after its flushes"
SM1
"Replace float valve in toilet cistern"
SM3