If You decide to do the flight control check before starting to taxi, You are fully covered by Monsieur Airbusses books.
Originally Posted by FCTM-PR-NP-SOP-100-Flight Controls
"At a convenient stage, before or during taxi, and before arming the autobrake, the PF silently applies full longitudional and lateral sidestick deflection. On the F/CTL page, the PM checks and calls out full travel of elevators and ailerons, and correct deflection and retraction of spoilers. (...)"
Originally Posted by OM-B-PRO_NOR-SOP-10-All engine taxi at departure
"Flight controls - Check.
Layer 2: Check the flight controls at a convenient stage, before or during taxi."
If You adjust Your seat in reference to the red/white balls and Your armrest in accordance to Your habitual letter/number, You can expect the setting to be suitable. Also, it is not forbidden to try moving the sidestick before startup/pushback to check/fine tune Your seating position while the aircraft is standing still.
Personally, I do the flight control check during taxi whenever there is a long, clear, obstacle free taxiway on the cleared route. In case of a complicated taxi route, an unfamiliar field, nasty weather or anything else that requires attention during taxi, I do the check before calling in for the taxi clearance.