Why do third parties do better in the UK, when compared to other countries with FPTP?

Ok so I am a US citizen that has been watching the elections of a few countries that have similar electoral systems to the UK, main example being Canada, and I have noticed something. The UK has way more semi successful non geographicly locked third parties (so not a party like Plaid Cymru in Wales, or Bloc Québécois in Quebec). This is not to say that you do not have the same problem as all other first past the post systems but that it is somehow elevated by something. Do you guys have any idea about what mechanism causes this or is it just a matter of political culture?