Range from the cheapest building of a retaining wall £270 (Portobello Projects based in W11) to the dearest building of a retaining wall £500 (Royal Stone Care based in W11).
Comparing builders estimates for building a retaining wall 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 to build a retaining wall in W2 by posting a job with HaMuch and we will send it to builders in W2.

"Build 2 retaining walls. the back retaining wall is about 70-80cm. The front retaining wall is 90-100cm. the two side flowerbeds are around 60cm. The two possible new side walls would be the same height as the front retaining wall."
CAMDEN