Thanks, CONF_iture and mm43, for the schematics.
Yes, they both confirm that Spoilers 1 perform as Speedbrakes as well as Ground Spoilers − clearly disproving my contrary suggestion. Sorry if I put the cat among the pigeons, but we now have some useful extra material to refer to. (In the cockpit, if selected, the F/CTL page of ECAM would clearly show this during Speedbrake operation.) It seems the air-braking capability of this A330/340 wing is quite powerful.
Chris