As a canadian, this is interesting, because i always thought our system was a copy of the UK system, but our courts strike down laws for being unconstitutional all the time.
It is a copy. The UK has a constitution. The UK constitution just isn't a simple document one can hang on the wall. The UK constitution is a body of knowledge and traditions. Recognize and do something a particular way for a few hundred years and it can become constitutional irrespective of whether it was nicely codified in a single document.
One can even say that the US and Canadian constitutions don't actually say all that much. They survive because they are so open to interpretation by courts ... which makes the body of constitutional knowledge needed to render decisions not all that different than that needed in the UK.
Most people understand "a constitution" to mean something written down that you can point to, that has the force of <something> behind it, that cannot be trivially elided by a government.
None of these are true of the UK "constitution", whether it is one document or 5000 precedents.
Any document written in a spoken human language will be open to interpretation - there's no getting away from that, regardless of the language, culture or country the document comes from. I still consider that a step up from the bullshit assemblage of "constitutional law" that claimed to be "the UK constitution".
One can even say that the US and Canadian constitutions don't actually say all that much. They survive because they are so open to interpretation by courts ... which makes the body of constitutional knowledge needed to render decisions not all that different than that needed in the UK.