I have had problems with Cometic gasket not in Cars but in bikes and not good i can tell you.

Can you hand on heart say you have supplied and fitted over 1000 YB head gaskets?

Not haveing a dig but 1000 ??? how long have cometic been doing car gaskets ? 3 years max 365 days in a year x 3 = 1,095 thats 1 a day for the last 3 years