Drive time Maidstone to Heathow

7:00 might be better. The M-25 is a wildcard and it will be very busy that time of day since you’re heading towards London. The closer you get the more congested it becomes.

Getting to the rental return is pretty p easy, but you could get turned around and have to loop back around. Once the car is turned in the ride to the terminal is about 10 minutes.

I’ve been on it when it moved just fine and also when it was a parking lot. Weather, construction, accidents will all contribute to the congestion.

Weather is dry and warm. I’ll start monitoring traffic about 6.

Have to add, not driving in Ireland or England again, it’s just too stressful.

Your issue is that, whilst it might be doable in 75 minutes it could equally take double that and you don't want to add the stress of finding yourself in stationary traffic to the street it sounds like you're already finding driving here. I think I would be aiming to leave around 6.30 to 7 and if you get a good run treat yourselves to a nice breakfast/brunch when you've got into the airport and through check-in and security.

Google maps says it could take anywhere between 1hr20 and 2hrs20. I’d go with the higher estimate to be safe.

Thanks, try to get out before 7:00.