Agree with DRUK. Park up and then walk into the arrivals hall with mobile in hand, it is the least hassle and the cost is minimal by comparison. I agree that there should be no cost but it is all part of the 21st century pricing model of pay-as-you-use, as per South West Air and all who followed.
When I 'loiter' for a collection at any airport, I usually choose a petrol station or layby outside the perimeter and wait for the call. However, you sometimes have people making their first visit to the UK, or elderly relatives so I just pay the parking cost. Air travel is expensive and Life's too short.