Very few countries, anywhere in the world, prohibit tourism (or place hurdles in the way of tourism) through criminal convictions. The only one where a criminal record can be a major issue is the USA. (Your own country also places a theoretical ban upon anyone with criminal convictions, unless they've been 'rehabilitated', but doesn't actually ask tourists any questions about them).
Canadian passport holders don't require a visa to enter the UK. You'll just need to fill in a very simple 'landing card' (which only asks a few basic questions, such as the address where you'll be staying, and makes no mention of criminal convictions) and show your passport.
Similarly, Canadian passport holders don't need a visa to enter the Schengen area, and there are no other formalities. Anyone who is in a Schengen country, irrespective of their nationality, is free to travel to any other Schengen country without any border formalities whatsoever. (They've been abolished throughout the whole of the Schengen area). A full list of countries within the Schengen area can be found here:
http://en.wikipedia.org/wiki/Schengen_Area
Chris