All bar one single Air Transat A330 are 9 across in a 3-3-3 layout. The seats are tight to put it mildly.
The only A330 that is 8 across is C-GTSD an A330-300 in a 2-4-2 config so you may want to bear that in mind before deciding. You have a 1 in 20 chance of ending up on that aircraft.