Very interesting about the squawk ident. I have always been taught not to reply to this instruction unless there was a new transponder code given. (i.e. squawk 0470 and ident)
A/C: LONDON - ABC123 - PASSING ALTITUDE 2300FT - CLIMBING TO ALTITUDE 3000FT - SAM2V
ATC: ABC123 - LONDON - CLIMB FL80 - SQUAWK IDENT
A/C: CLIMB FL80 - ABC123
Had a look through CAP 413 and couldn't find anything. In the supplement in the Climb-Cruise-Descent section the last instruction is to squawk ident but they don't give a reply.