Range from the cheapest Downlights installation £240 (Robin Greenfield based in HP10) to the dearest Downlights installation £440 (Zamir Mohammed based in SL1).
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 SL6.