Every country in Europe has slightly different rules and regulations, far too many to list here. Some are silly, some are sensible, others are downright bizarre, but the common problem with most transgressions in European countries is they can leave you with an on-the-spot fine and a painful hole in your wallet!
Luckily however, the BMF has a handy page on their web site containing a pretty useful guide to all the requirements for motorcycling in every country in Europe. Have a look
here.