Imperial Miles for me. Why would you settle for only 5/8 of a unit when you could have the whole thing? Like steel, it's real. I suspect riders who take part in competitive aspects of cycling have got used to kilometres because it's UCI compliant. Out in the real world, when I'm going somewhere in this septic isle, miles are what are on the signposts. If I go across the Channel I'm quite happy to use their kilometres. When in Rome, etc.