10W, thanks for the explanation, easier to understand the system now.
The lastest jepp chart I can currently find no longer says that Scottish will issue a clearance to aircraft filing over RATSU, as PPrune Radar and 10W have clarified. I seem to remember that on our UK to Iceland leg we received a departure to a filed waypoint from clearance delivery. However, assuming we were then cleared flight planned route, and that Scottish would issue a revised clearance if necessary, we did not call Reykjavik oceanic prior to RATSU, the entry point. At this point (RATSU) we were asked by Scottish to contact Reykjavik, which we did and were given a slightly revised route, but no assigned mach/flight level (not too surprising, I guess). Everyone seemed happy....
Question then for PPrune Radar or 10W, (or others with knowledge) based on this scenario, the next time we do such a route;
Should we have called Reykjavik prior to RATSU then, passed ETA, and requested mach/flight level?
And that we didn't is a big NO NO?