Range from the cheapest EICR Landlord Certificate £132 (Hemiko based in SE1) to the dearest EICR Landlord Certificate £285 (Cole Electric based in SE11).
Comparing electricians estimates for completing an EICR test in your home 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 by posting your job to electricians in SE17

"EICR Landlord Certificate 5 years renewal. SE5 I'm unsure if the electrical box needs replacing. Apparently, those located in fire escape routes require replacement. But mine is on the wall in the hallway, so it doesn't block the way when walking. It's top floor of an old conversion flat."
SE5
"EICR test 28 sqm 1 bed flat"
SE1