Cvh heads with hardened seats from the factory started with the 88SM part number. Eg 87/88 onwards.

An S1 head will be 81SM as standard so unless they've been changed it won't. I used castrol valve master in my daily s1 for years and it ran sweet as. There is 2 versions, standard and octane boost. I used the latter, with premium fuel, pretty much as close as you can get to 4-star without paying silly money