Capt. Fathom
Have to disagree with you on both!
"Leave control area descending" is a level instruction - you are instructed to vacate your currently assigned level. If you don't believe me, try maintaining a level you've been cleared to leave descending and see what ATC reaction you get! In the strict sense of the AIP it is a level instruction because you're being told to bugger off from the one you're at - irrespective of the one you're heading for.
"Visual Approach" I agree is a manouvre but is not one you can undertake without a clearance - therefore "cleared visual approach" definately requires a readback (vis 'e') - it is a clearance to descend from your currently assigned altitude (but not to climb) and to manouvre from your current heading/track as required. Again, try doing either without ATC "clearance" and see what happens. Again in the context of the strict AIP, you're being given your approach clearance - without it (and in the absence of an instrument approach clearance) how are you going to make it to the runway without many tedious instructions from the controller - all of which would require a readback.
All of which proves the orginal contention - that nobody really knows what the readback requirements are!
UTR.