Just to give some feedback from our trip....

We took the taxi both ways after some helpful advice on here. The way to the hotel was fine. The driver had a CNG/LPG tank in the boot, along with the world's largest subwoofer, so the cases went on the front seat. It was easy to demand the meter in that direction, as it was from the airport

It was slightly confusing at first paying the driver the toll charges, but they were 45 Baht, followed by 25 Baht. Total fare was about 270Baht from memory + the 50Baht airport charge

On the way back to the airport the driver demanded 500Baht including tolls. We laughed and asked for the meter. He argued - we told him to use the meter. Once again, it came to about 270 including tolls.

The drive from the airport was fine (120kph ish) - but to the airport was scary (140kph) as another taxi driver didn't seem to like ours, so kept accellerating and cutting us up and braking. Not pleasant.

We were quoted 950Baht for AOT in the cheapest form of transport.