I agree with above, I've noticed the A320 family particularly the Shamrock's cut the corner. For me, it's most noticeable at EXMOR when they're coming up from the South then cutting left to STU for EIDW.
Doesn't bother me, I know they're going to do it and if there's a separation issue they'll be on a heading anyway. Plus I know I can ask them to overfly the point before commencing the turn should it be needed.
As to the original question, if I ask an aircraft to leave a point heading it generally to set them up with some form of separation before I actually need it so I've got time to fiddle with it if needs be.
In my head that all made sense. so hopefully it does here