Range from the cheapest Downlights installation £190 (County Electric based in B44) to the dearest Downlights installation £390 (Electroplumb Ltd based in WS2).
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 WS1.