Heard this the other day...
ATC: Propflier 9876 expect further climb in about 10 miles due crossing traffic descending to 1000ft above.
Propflier: Roger, expecting further climb due ... err ... in 10 miles ... for crossing traffic ... um ... 1000ft above us Propflier 9876.
Meanwhile we are about to hit our clearance limit waiting to call in on the frequency.
As an aside Jeppesen says the following about calling for P/S in Heathrow:
Phraseology should be: callsign, ACFT type, stand number, ATIS letter, QNH and "fully ready, request start-up"
S.