Range from the cheapest Downlights installation £270 (Alpha Papa Electrical Services based in EN8) to the dearest Downlights installation £590 (Caspian Electrical based in EN9).
Comparing electricians estimates for Downlights installation 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 for installing downlights by posting a job to electricians in EN9.