Student controllers are taught what the MATS Pt 1 Section 3 Page 2 Para 9 which says:
9.1 The position of an aircraft is to be passed to the pilot at least once on each leg of the circuit.
9.2 Position information for an aircraft making a straight-in approach is to be passed at least once before it commences the final descent.
Note that the phrase "is to be" makes it mandatory.
That of course is the bare minimum required by "The Book". We also teach that, providing the spare capacity exists, number in traffic is useful, a/c type ahead if particularly slow or heavy can give a clue. We also teach that good practice is to give track-miles to touchdown when turning base leg, when turning onto the closing heading, and immediately before QSY to TWR. A good radar controller will be keeping an eye on the Mode C and adjusting the track miles accordingly.
It is to be hoped that on first contact the pilot is informed what sort of approach he will be making e.g. "Vectoring for an ILS approach RWY 26". However, one must accept that when the R/T loading is approaching 100%, the important stuff, like stopping planes banging into each other, takes precedence over the nicities of how far you have to go and what that boring aircraft is you are following. Believe it or not, we do teach that a well informed pilot is less likely to ask questions and is more likely to do what he is told without quibble, thereby making every-one's life easier.
In the interests of PC, any reference to the masculine gender should be taken to include the feminine gender also.