Saphs in the UK always had the seperate grill (mind you, its design changed slightly with the 90 facelift), while Sierras always had the "long bonnet".

In mainland Europe there was never a difference between Sapphires and Sierras regarding the design of the front end. Until 1990 all had long bonnets, from 1990 on all had shorter bonnets (seperate grill as you call it).

This goes for all models except Cosworth and (I believe) P100.