Waited nearly an hour at Heathrow Airport due to the crowd; I got a manual car which I don't think matches the model I paid for.

Upgrade to an automatic was very welcome for London driving.

Like: Pleasantly surprised by how helpful the Europcar office staff were with limited upsell.
Dislike: I got slightly confused at Heathrow T2 over which bus stop to use for the shuttle - some better signage that can be seen at a distance would help.

Like: Well priced for size of car, well known rental company, quite a simple process overall.
Dislike: Car booked was a Skoda Superb or similar, which is quite a large car. Car issued was a Skoda Octavia, which is the next size down.

Like: Service staff AMINAH at London Heathrow pick up was excellent. Friendly and efficient...even though it was near Christmas and I arrived at a time when the colleagues were going to take a group photo, she helped out immediately and was very friendly and helpful. Good job Aminah and thank you!
Dislike: Returning the car was a pain. There was no transport back to civilisation. I had to struggle to get out. If there was a courtesy bus back to the Terminals, nobody told me!!!! I walked and walked to find a bus stop to my hotel.