The issue about cleared to ender CAS in different countries is interesting and practices vary.
In the US, to enter Class C and D two way radio contact only needs to be established (use of each others call signs). The word "cleared" is not necessary. However to enter class B a positive clearance is needed.
It seems to me that the UK operates class D like the US operate class B.
I dont know what the Irish rules are re class C or the French rules re Class D