Cheers for the replies.
I appreciate that skipping across an uneven surface can cause the TC to trigger but this is more like a continuous activation of the TC for as long as I'm applying the throttle - take foot off the pedal and then reply and it starts back up again.
The fact that the power is cut for the same duration seems to suggest to me that the TC thinks the wheels are spinning (whether they are or not).
From what some of you say, maybe there's nothing to worry about and it was just a few incidences of poor road conditions.
BTW - I'm running on 18's with Pilot Sport runflats, good amount of tread (7mm). Out of interest, would you recommend Bridgestone RE050's for the 330d? Found them to be good on my 120d.