Thanks for the advice guys, L3nny, think that might be pushing it with a pillion bearing in mind it's my first Euro trip!
Been looking into it further, and when you consider that I live up in Yorkshire, the worst bit of the trip will be the M1 slog down to the south, which will take a full day's riding either end of the trip, plus a night in a hotel at each end.
SO, we figured it might be more relaxing to nip to Hull on the friday night, overnight ferry to Zeebrugge, wake up refreshed and ready to roll. This would also allow us to call into places like Brussels (where we might not normally choose to visit) on the way to the recommended eastern part of france.
Can't wait!
Ooooo, another question - leathers (and waterproofs in luggage) or textiles?