Ah, this does make another useful safety point, about the difficulties over multiple units in aviation.
In the spirit of Ghengis' comment, I once flew an Arrow all the way down final, in the USA, pegging Vref to a knot either way.
Unfortunately the ASI was in mph.
Regression to prior experience is a wonderful thing.
The instructor checking me out wasn't worried, he assumed I was practising a performance landing.
I haven't done the same thing since.