Helpand advise needed!

My alarm was going off randomly which was really ******* me off. Took it to VW who said driver side needed new door lock £300. Took car home alarm still sounded so to it back to VW today.

Got a call from VW. They want another £261 to replace the door motor. I said what about the door lock i paid for? They said the motor and lock are interconnected and the lock would have need to be replaced anyway.

I need to complain! I got the service managers name to whom ill be writing a letter. I need to get my car fixed. Do i agree to go ahead for the job then seem reimbursement or complain first??