We used Chailease auto rental service-Taipei.
Tel 02 2828 0033 Fax 02 2826 2191.
We arranged everything in advance over email:
[email protected]
They are not actually at the airport but will deliver and pick up there or at a hotel (we picked this alternative) including after hours, for a fee (between 500 and 1500 ntd, depending on when and where). Their rates seemed reasonable and everything worked as promised. The only issue was that after we rented the car, torrential rains closed the roads we were planning to travel on. We were unable to reach them to return the car early (they didn't answer their phones for a whole day, but it was a day that schools and government offices were closed due to the rain). So we had to pay the full amount without actually getting to use the car as planned. I don't think this should be a mark against them, though, since it was a factor out of their control and the contract didn't provide for this contingency.
The person who delivered and picked up the car spoke perfect English, and all our email communications were very clearly conducted in English. The rental contract was in English as well.