My local dealer charged me for work that wasn't done - what can I do?

My local Subaru dealer recently charged me £400 to replace the spark plugs on my 2005 Forester. They charged three hours labour as they reckoned the plugs were seized. The car was still idling badly so I took it to a specialist who spent hours trying to sort out what was wrong. Eventually, he checked the plugs and found that two were seized in so obviously they had not been replaced by my local dealer. The specialist suggested two options - either I take the car back to my local dealer to get them to complete the job, or he could give it a try, at the risk of the plugs breaking or damaging the threads. In a worse case, it would involve removing the cylinder heads which would cost around £1000. I no longer trust my local Subaru dealer to do this job properly so could I get the work done by the specialist and then try and recover my costs from the local dealer? Should I ask my local dealer to complete the work properly, as they've invoiced me for it, even if they have to strip the engine? I'm furious as this has taken up hours of my time when they should have simply admitted what the problem was straight away.
Send a letter by Post Office Special Delivery to the dealer that charged you £400 demanding that it either completes the job he fraudulently billed you for or refunds the £400. (They probably tried to remove the final two plugs, was afraid of breaking them, but nevertheless should not have billed you for work he did not do). Keep a copy and staple the certificate of posting to the copy so it becomes a matter of record for Small Claims if you later need to make one. Be aware that if the other specialist undertakes the job and the plugs snap you could be in for a lot more than £400 to remove the engine, separate the cylinder head (or heads if the stuck plugs are in both banks) and machine out the failed plugs. Do not attempt to charge for your time wasted. Be aware that the dealer will claim that poor maintenance prior to being given the job was the reason he could not extract the plugs.
Answered by Honest John

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