You can book a taxi via following methods:
Online: http://www.dovelincars.com/
Telephone: +44 188 956 7055
Yes, it's possible to pre-book a taxi with Dovelin Cars, please contact the company.
Dovelin Cars has both regular and air-conditioned taxis, please mention your preference at the time of booking.
Please contact the company on their helpline number to make any changes.
Generally drivers will meet the passengers at the arrivals on airport pick ups but do check with the company.