Regarding levels, again we do this to traffic receiving a RIS joining the airways system, they are allocated a level at which they are to enter CAS at, they choose when to climb or descend but they must be at that level by the airspace boundary.
But would you instruct the pilot to climb/descend? If the pilot is issued with such an airways joining clearance, he has to climb to that level anyway, even if he's not under a radar service at all.
MATS 1 says,"Controllers can expect the pilot (in receipt of a RAS) to accept vectors
or level allocations which may require flight in IMC." Under RIS, it only states, "the controller may provide radar vectors for the purpose of tactical planning or at the request of the pilot." No-where does it say anything about allocating levels. However, whenever this subject is raised, and the question is asked, the answer always comes back as an emphatic "Yes, you can issue climb/descent instructions to aircraft under a RIS". Where does it say this? Or am I just stuck in the past, when things were so much more simple, i.e. RIS meant you watched 'em on radar, passed the traffic, and let them get on with it. No headings, no levels, nothing. If you wanted to be told go left, go right, go up, go down, it was a radar advisory service.