And whilst on the subject - If we give a climb above the SID level - do not ask "is that unrestricted?" - It means climb now! The new clearance negates the old.
I'm sure the new clearance negates the old in the UK but some of us fly into a lot of countries and that is just not true many places. If you're going into PEK and are given a lower altitude on the arrival, you are still expected to make published altitude restrictions unless they tell you otherwise. Some crews have found out the hard way about this detail in recent years. It is buried somewhere in the country pages of the J-Aid but who has time to read that stuff.
A similar situation exists when you are cleared to taxi to a runway. Some places, like the U.S., you have an inferred clearance to cross other runways to get to the hold short line. Many other places, you don't so, similarly, American controllers get testy when you ask for clarification.
It would be great if I could memorize all the little nuances of local ATC procedure everywhere I go but in the real world, if I have any doubt about a clearance, I ask rather than assume.
I too have felt that a higher Nationwide Transition level , like FL100 would maybe help resolve some of the problems, but against that Air Traffic would then have to be updating the Altimeter Setting as you progress along the SID, STAR or vector.
It may be hard to believe but we've flow SID's STAR's and vectors for many years in the U.S. with a FL180 transition level. If you need a new altimeter, check the ATIS.