To use 'were going', either (a) you are in France (or in Brighton for a dirty weekend and 'business trip to France' is your cover story), because the 'going' part stopped as soon as you arrived in France or (b) you are back from France and this is a 'post mortum' conversation as to whether he has got away with it! If you haven't left for France yet, it is still 'are going'.
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