From CAP 413. It's not terribly clear but might provide a clue:
1.3 Departure Information and Engine Starting Procedures
1.3.1 Where no ATIS is provided the pilot may ask for current aerodrome information before
requesting start up.
1.3.2 Requests to start engines are normally made to facilitate ATC planning and to avoid
excessive fuel wastage by aircraft delayed on the ground. At certain aerodromes,
along with the request, the pilot will state the location of the aircraft and acknowledge
receipt of the departure ATIS broadcast identifying letter together with the QNH.