......and another thing, ......... don't forget the listening squawk !
dial this in for a few minutes before initial call up, especially if you are close to the zone boundary. Expect that there will be a delay before any crossing clearance would be issued, due to ,IIRC , co-ordination between the LGW App controller ( Swanwick ) and Twr ( on airport) for traffic separation.
My experience is that mid afternoon is a good time to request and obtain a crossing.
Transponder Code .............Gatwick / Thames 0012
Solent / Bournemouth also will be implementing a similar listening squawk from 28th Jan 2010...........see ....
FLY ON TRACK