London TMA airfields - in some cases the tower validates and verifies using the aerodrome traffic montior, in others not, depends on the kit at the field and the integrity of the link to the centre. If tower does it we don't need to, if not you'll be asked for the ident (in theory before being given any executive instructions, in reality we all know waiting isn't realistic given airspace complexity and frequency loading etc) Luton validates and verifies, Stansted and Heathrow don't, can't speak for Gatwick! I assume the Scottish airfields don't validate and verify.
Worth remembering too that by the ketter of the law, unless you ident in response to a request to do so, it doesn't count as identifying you, so we *should* wait for it to stop, then instruct you to do it again, all before giving any instructions. But is the SID that long?!