Heathrow is the most popular as well as the biggest airport in the UK, which means there is plenty of parking space there but you may still need some advice before looking for a slot. The best thing you can do is look for parking spaces where you will have the chance of finding the cheapest deals when it comes to Heathrow airport parking. By booking a parking slot at Heathrow online you might end up saving up to 20% which is incredible because parking at this airport in particular is usually very expensive as there security there is really good.