I consider this practice rude, and always make the effort to find an appropriate passage to to opposite aisle. (Unless the seats are vacant, of course.) This is the main reason that I do not book center bulkheads.

As to the US A330, I have recently flown three transatlantic segments on this a/c and have not noticed and pax or crew crossing in front of the center bulkhead seats (unless vacant). On each of the flights my companion and I were seated in the bulkhead window/aisle seats (either 2AB or 2GH). If you like center bulkheads, I would book the seats, you are bound to enjoy them.

The only other thing to note is that the F/C section on the A330 has limited overhead space and sometimes the F/C pax bags are stowed over the bulkhead seats in Envoy. There seems to be enough space to go around, but if you are late to board your overhead space may be gone.

CWPFLY