Is my mechanic ripping me off?

I took my 2005 mk2 Ford Focus 1.4 to the local garage the other day to get the engine looked at as it's making a knocking noise.

He first of all told me that the engine sounds so unhealthy that it's on it's way out, so he looked at it and told me that the hydraulic tappets are warn out and need replacing. He then told me it will be £800 to replace all of them.

They are a good garage done get me wrong, fixed my parent's cars fine without problems, but I've been doing a bit of research and something just doesn't seem right.

The car is going back on the 13th July to get fixed, is it worth it or am I being ripped off?

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