when are the busiest times at the LHR clubhouse[?]
When i have been there over the years, the morning seems to be the busiest time of the day. Around 9.30 till 12ish you have aload of flights going out to places like IAD, JFK, SFO, LAX, MIA. Also at 10 and 11 (i think) gulf air has flights going out. They use the CH also.
Also in the evenings it gets a bit busy. From 20.00 to 21.30 there is 6 VS flights. EWR, DEL, BOM, JNB, HKG and from march DXB