MATS pt.1 says that ATCOs can only use the ident feature as a method of identification when using SSR 'when it has been requested' by the ATCO. See CAP493, Section 1 para 4.1 sub-para c).
I even read the Scottish MATS pt.2 as saying that we can only satisfactorily accomplish identification, validation and correlation of code callsign if we transmit the instruction to 'Squawk Ident' and then the symbol appears around the a/c position symbol.
Therefore, I think that you should only squawk ident when requested. I know that there are quite a number of crews who call up and state that they are 'Squawking Ident' when climbing out of PF or PH. This seems to be a peculiarity of ScTMA deps and not something that I've encountered elsewhere. I don't think that it really cuts down on radio calls at all and I, for one, would rather that you pressed the button only on my explicit instruction!! :-)
Any other opinions?
Regards
TSA