Reading through this thread and it seems to me that some people are getting confused between IFR and IMC. As far as the ATCO is concerned the general point that is important is IFR or VFR as this sets what level of service you can get. Now as for offering extra if someone is IMC that comes down to duty of care. If the aircraft is in an area of high ground then you give the minimum height to fly and then work out how to get them VMC again but if you want a seamless flight with controller to controller fly inside CAS the whole way otherwise get what you can outside. Possibly harsh but my 2p's worth....