Anything comprising a loco and coaches will use flags and lamps. To my knowledge, no locos are equipped with bell/buzzer communication (unless the 68s/88s have that feature?).
Some of the 59s had or have door controls compatible with 377s. Not sure if this included bells, but it would make sense.
I understood that a green flag and possibly a red flag, lamp and whistle were part of the Guards/Conductors case/bag which they get when they sign on for duty.
Required equipment usually includes a torch capable of showing red / green / white, a red flag and a green flag. (Yellow flags, and torches with yellow aspects, are carried by some staff, but not usually guards).
A whistle is not part of the dispatch process in the Rule Book, and use of whistles varies from "discouraged" to "mandatory" depending on local customs and special instructions applying to various routes, traction types and depots.
Conductors / guards usually get given a personal-issue bag which contains all this, and more, which is their responsibility to keep stocked, and bring to work at the start of each duty. Obviously there are spares for the forgetful (and for those not in favour with the depot administrator who supplies new stuff
).