Nice bikeshop near De Panne which is a stones throw from Dunkirk, its called Jochens Veldrom. I have been there, some nice bikes and parts. I understand there is another bike place (not Jochens) in Calais but never been to it, they are a Gitane Dealer and a few other things.
Jochens had a good selection of Bikes such as Colnago, Pinarello, and the stuff they were displaying was across all ranges, going upto the 7k€ and plus. don't think the exchange rate from £ to € is in our favour however.
That said, they had a lot more good parts off the shelf than many I have seen in the UK.
A good few places to eat or get food nearby, always worth a visit.