Hi Torque,
The recent changes to the sector airspace only introduced NELBO to this route, there were no CAS base changes to this particular part of the route.
The airspace along the route you were following has (and has had for at least the last few years) a stepped base, FL195, FL135 and lastly FL75. Each section being approx 10-15 miles in length as you track towards NELBO. Hence why you will often get cleared to FL200, then FL140 before being cleared to FL100 (Our agreed level for transfer to Aldergrove).
Some pilots don't seem to be aware of these bases, and indeed most aircraft can be cleared to FL100 early because the controller knows their descent profile is unlikely to drop below these levels.
Some operators however seem to descend earlier, and you should get a warning like you recieved or the controller should offer you a service below CAS if you wish to continue descent or you can level off briefly to keep you inside.
First post, so hope this makes sense
