Range from the cheapest Downlights installation £361 (Luke Sabarta based in NW9) to the dearest Downlights installation £390 (Custom House Improvement based in Nw9).
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 Colindale.