Hi Ray,
the Olhain castle does not offer accomodations.
In the list which Rufus linked above you find a gite in Houdin.
I stayed in the Hotel Le Cottage in Bruay la Buissiere, Tel. 03.21.53.14.14. The hotel is about two kms away from the VF.
From the centre of Bruay la Buissiere there is a bus line to Houdin where you meet again the VF.
The next accomodation after 24 kms was a chambre d'hote, new name:
Le Goût des Hôtes 68 Rue Marcel Lancino, 62153 Ablain-Saint-Nazaire, Frankreich•+33 6 80 95 25 89
BC
Franz