Lesley, I asked a similar question a few months ago when I booked to go to Arillas.
The sortof answers I received were that it all depends.
Time of day;
Number of Tourists coming onto the island;
(and therefore) how many stops they need to make in order to get you to Arillas.
The sad thing is that road wise, Arillas is at the other end of the Islan from the Airport and most other members seemed to think anywhere from and hour up to 2.
Im also with Manos but flying from Stansted.
Hope that helps.
Giff