from what i can gather, there's quite a few different companies who do this. I'm looking for a reliable company who won't dictate when they'll meet us by our check-in times. I like to get into the airport early!!!
They were waiting when we pulled up, and then had the car outside as we emerged - the only tricky bit is that they like you to pick the car up again at Departures (because they can't hang around outside Arrivals?) and it's quite hard to find Departures from the inside (luckily I had an ex-Boy Scout with me )
From reading some of the comments though it looks as if you have to drop off in a car park now - since the Glasgow airport incident - which isn't going to be as convenient. But most comments are still favourable.