I found out that in EGLL the procedure is quite similar. The difference is just for having two ways to transmit the departure clearance: via data link or via radio. Via data link the departure clearance is available since 25 mins prior the EOBT, via radio 15 mins if pilots have been briefed with regard to the correct phraseology (???
). All other pilots must be fully ready before calling Delivery frequency, so the same as in Italy.