<<usually at the platform height (sometimes a little bit above) when we are given a further descent, and to descend with the glideslope. It just seems to be a bit more than is necessary, especially at big international busy airports.>>
Know what you mean - done it myself millions of times.. The SSR indication suggests the guy is still above the GP so ATC tends to keep them coming down to the next 500ft interval, perhaps in the belief that this would put them under the GP, where we're told most people like to establish from. Maybe this stems from experience with the odd pilot who, when told to "descend further on the ILS" retorts "but we're still above the glidepath". You can't win!