All proper British people mix units. Fractions like 11/32" are just too hard, so you switch to millimetres when things get too small for inches. Metres are just French yards.
The one that can catch you out is using lb-ft instead of Nm on a torque wrench; they are close, but not close enough that you won't get in trouble by using the wrong set of numbers. Oh well, I never wanted that cylinder head anyway.