"On request of the next sector, fly heading..."
do we really care which ATCO is asking for the heading? surely its a seemless service?
but thats so we don't look like the numpty who needs the heading!
i do use "at the request of the next sector" when i've cleared you to your cruising level and the next sector can't take you at that level at short notice. Its to say i would get you to your requested level if i could but the next sector won't let me.