Carlos Davila has been making these maps for quite some time: http://alternativaslibres.org/en/trucks.php.

I know he made some maxheight edits in the UK, so he would be the person who would know if feet and inches values in maxheight are readily useable. (Personal gripe maxheight:imperial is a bad tagname as the largest country to have feet/inches values is the US which left the British Empire before the (British) Imperial standards of weights and measures.)