MT, did you drop off your friends right in front of the airport building or to the side where there is a very short term car park and drop off point? I only ask because the drop off car park gives you a free 10 minutes. Passengers  walk through a short covered walkway and enter into the arrivals area. It's such a small airport that everywhere is a short distance to walk whether for departures or arrivals. 

I've used BA several times and usually use a small local car park to park up for the duration. The owners have a people carrier and drop me off in the above car park and when I arrive back I call them after I've passed through baggage collection and they send out a driver to pick me up. They just whizz in, load up and off they go without being charged. If you are collecting your friends you might want to suggest the same to them to save you the £1.

As for other airports, I've not heard of people being charged just for a drop off either at Gatwick or Heathrow, although it's not always possible to "drop" people off at T5 H/row as they only allow buses to drop off.