Range from the cheapest replacement of a toilet float valve £25 (Kaloyan Vasilev based in E16) to the dearest replacement of a float valve £80 (LTT plumbing based in E1).
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 E14 9 by posting a job with HaMuch and we will send it to plumbers in E14 9.

"Replace float valve in toilet cistern and flush button."
E16