From what I can tell, UK customs is barely checking imports.
EU nations, however, are being rather thorough on checking imports from the UK - though this varies from country to country.
Not just UK, although I did get charged 16€ for the calendars of my grandson that my daughter sent over as christmas presents. I forget their quoted value but from memory the duty plus La Poste handling fee was about 40%.
But we are also getting charged now for stuff from Thailand that got through before. I am waiting for a SA brake hub from (I think) Taiwan, it's coming through China. We'll see how much that costs me.