My boss has a focus 1.6, His engine light came on so took it to a local garage who informed him (from taking a diagnostics reading) That his Lambda sensor was on the way out. He said he had fixed it for now but one of the two sensors had failed or was failing and this would be around £400 to fix (as he advised both would need replacing) if the engine management light came on again.

This morning the light has come on again, so just querying if the price quoted is too much?

Any help/advice would be greatly appreciated