I have never worried too much other than Documents and a GB sticker (or a Euro numberplate). Wear a helmet and watch your speed and don't do anything stupid and the police have no reason to bother you.
As far as I know France has dropped the breathalyser thing as well as the hi viz requirement. There's something weird in Spain about Sat Navs and also about spare spectacles but not sure if it all applies to bikes.
Sorry, not really much help. Any specific country in mind so any locals or ex pats can help?
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