Aero-fleamarket: I agree with the Capt on this. I believe under the terms of the clearance, what he did is permissible. Of course, it all depends on where you were when this occurred. As tolgab says, there shouldn't really be a problem, as the terms of the clearance don't assure separation with anything other than at the restriction.
zkdli: Is there a requirement in the UK to continuously descend, once descent is commenced (even under a "when ready")?