I've been visiting the HTF on an almost daily basis for the last six years, how could I have missed this one?! *Heads off to use the search function to dig up questionable threads* :D
I'm not British but I'll offer a European perspective. Fractions are of course used frequently in many if not all European languages, but not usually in measurements of length as you correctly assume.
God no. It's 7 centimeters. Maybe 70 millimeters. You would only use 69.85 millimeters if...