"Blocked" is fine.
"London Fastjet123 request" is the way i'd prefer it. It gives me the option of choosing when to answer.
In a busy RT environment, i'd rather pilots did that than launching into their request straight off. a) i probably won't be expecting it and then miss either the callsign or the request and b) it'll probably happen right when i need to do something and screw up my plans.
If i can answer when i want then it'll enable me to control the RT much more effectively, which makes for a better service all round.
