You really have to be realistic. If the machine is not intended as a show-piece but as a useable mode of transport/fun, then why not use whatever is best/easily obtainable.
If a metric nut and bolt can be used where a Whitworth, or whatever was, then use it. Not everyone walks around with a micrometer or vernier guage and is about to pounce on your bike with a thread pitch guage.
It's about doing a "good" job. As the Imperial stuff is readily available there's no excuse for fitting metric fasteners.
As someone else has said, if nothing else it means only one set of spanners needed, and that's apart from the rather obvious metric bolt markings (ie no vernier needed).
If, as some would like, you go for purity, then you should have crappy tyres, crappy lights and ride with goggles and a cork helmet/flat cap or none at all.
That's taking the debate to the ridiculous extreme....
Originality has it's place but practicality and common sense must prevail.
Agreed, but there's STILL no reason to fit metric fasteners......
