From latest CAP413
Automatic Terminal Information Service (ATIS) UK
4.184 To alleviate RTF loading at some busy airports, Automatic Terminal Information Service (ATIS) messages are broadcast to pass routine arrival/departure information on a discrete RTF frequency or on an appropriate VOR. Pilots inbound to these airports are normally required, on first contact with the aerodrome ATSU, to acknowledge receipt of current information by quoting the code letter of the broadcast. Pilots
of outbound aircraft are not normally required to acknowledge receipt of departure ATIS except when requested on the actual ATIS broadcast. If, however, pilots report receipt of a departure ATIS broadcast the QNH should be included, thereby allowing ATC to check that the quoted QNH is up-to-the-minute.
4.185 Aerodromes possessing ATIS, the hours of ATIS operation and the frequency employed are published in the UK AIP.
4.186 ATIS broadcasts (which should be no more than thirty seconds duration) will include all or part of the elements of the information shown in the Manual of Air Traffic Services Part 1, Section 3, Chapter 1, in the order listed