Although I'm not a UK ATCO, I'll have a bash at answering your question, from what I've heard from a friend who is in TC. CAP493 is also known as the MATS Pt1 (Manual Air Traffic Services Part 1). Now... every unit has it's own MATS Pt2. MATS Pt2 for the LTCC and for other units, such as the MACC I believe, state that to make handling of aircraft easier without having to telephone other units and co-ordinate like that etc, a heading should be reported off to the other controller. Because this is a MATS Pt2 document, it overrides what CAP493 says, for the particular unit. There are other things which are laid down in the MATS Pt2 which are opposite requirements from CAP493.
Regards,
G_F