Originally Posted by megaloman

Sofia will depart/arrive at T5 in December, so this should make your connection smoother as you won't need to take the bus between T3 and T5.

On arrival from Sofia follow signs to Flight Connections, there go through the domestic connections - you'll need to clear immigration there - then biometrics will be taken at the bp scan and you rejoin the queue for security. You need to arrive at the bp scan at least 35 minutes before your departure flight.