Also if you're not in a hurry to get parking booked, check the official airport website every week or so, because they quite often have unannounced flash sales. I've gone on to Heathrow's for example, found it a bit too pricey, then gone back a few days later to find it £50-£60 lower. Then another few days pass and the long stay is back up to its original price, but one of the other options (Meet and Greet for example) has come down considerably - maybe even to match the long stay price somehow.