We have taken many pax into Heathrow day and night in an AS 350 and have never had a problem with long waits ...in fact the ATC are so efficient there they nip you in and around all the traffic with great skill (none of your waiting on the ground for a plane on 10 mile final when all you want to do is depart at 90deg to the runway and can be well away when the plane is still on 4 mile final ..)
The other great thing about it is the fuel price which is cheapest in the country by a mile .