I used to change at transition in Australia, but Australia has a single, standard transition altitude of 10,000 feet. In Europe, with such a plethora of transition levels, it is smarter to change on receiving the clearance - it gives you a trigger to change, which makes forgetting (with the consequent level bust) a little less likely.
Where this may change is on P-RNAV SIDs and STARs, In this case limiting levels or altitudes may be published on the chart. You may be cleared on descent to an altitude, but with an intervening level restriction, so you need to define a point to change from QNE on descent.