Early morning transportation to Heathrow?

I've never taken this route but 2 hours should be enough (as long as you check-in online the night before and use the bag drop).
But it could happen anywhere that the train to the airport will not show up when you expect it to.

Two hours should be enough time for a Heathrow to Dublin flight, even if you have to check in and check bags. I see from Aer Lingus' web site that you have to be at your gate at least 30 minutes before departure for this flight, or you will not be allowed to board. So, arriving 2 hours early gives you 90 minutes to check in and get to your gate.

As for car services, I have no personal experience, but you can get quotes directly from them for the size of car you need, the exact address you will be leaving from, and whether you will be paying with cash or credit card (some have a substantial discount for cash). Three that are often recommended are Just Airports http://www.justairports.com/, Simply Airports http://www.simplyairports.co.uk/index.aspx, and Blackberry Cars http://www.blackberrycars.com/.

We always stay at a Heathrow hotel the night before an early flight. No stress about a late car service or a delayed train. We enjoy London then do an early check-in at our Heathrow hotel or get there and drop our luggage. We then like to go to Windsor by bus and spend the rest of the day until early evening, having a nice dinner and doing some wandering about. We lately have stayed at Travelodge Heathrow Central because it's in a nice neighborhood with pubs, shops, pizza joints and even a Polish deli. And the price is always right. The Hoppa bus to LHR goes to most hotels and starts running around 0430. Across the road is a Doubletree by Hilton if you want more upscale accommodations. Get on the Heathrow website and look at the hotel selections. There are many to choose from but most are relatively isolated and you are limited where to eat and likely eat at their restaurant. Works for us.

As George has suggested, staying near the airport eases the stress of getting to the airport on time. The many hotels along Bath Road, such as Travelodge Heathrow Central, are served by public buses, too. Use your Oyster card and it's only £1.50 per person for the bus ride to the airport. Bus N9 runs 24/7 and stops right there near the Travelodge, then continues along Bath Road stopping near many other hotels en route to the airport. In fact, if your hotel is between Harlington Corner and the airport, the ride will cost you nothing because you're within the free fare zone! The first stop at the airport is Heathrow Central bus station where you get off to walk (inside) to terminals 2 and 3, or stay on the bus through one more stop to the last stop which is Terminal 5.

Hi!

Thanks for the information so far. I would stay close to the airport, but I'm using my hotel points for a stay throughout the week, so that's not really an option.

Enjoy,
Gretchen

Two hours at the airport before your flight should be enough. However, if you want to use a car service I had good luck with this one:

https://www.airport-pickups-london.com/