Nigel,
One servo for two ailerons is much less than half of the current the two servos would use.
All lift forces on the ailerons will be compensated!. Play of course is a problem but we have good materials to make bell cranks for example.
I do not have any adjustable quick link on the aileron connections. Simple rules for me, design the normal throw with the max displacement of the servo.
Second rule is, use lot of movement of the connection rods, this reduces the play and force in the rod. Simple rules for me.
Succes
Cees