In Rouen, I stayed at the Hôtel Mercure Rouen Centre Cathédrale. It was right in the old center of the town and easy walking distance to museums, the Cathedral, Le Gros-Horloge, etc. It is a modern hotel, and they have a nice breakfast buffet, as well as underground parking if you call ahead (you have to actually drive in the pedestrian area to access it). As far as a base in Normandy, you don't mention what it is you want to see. Normandy is a large area and there is a big difference and distance between Rouen (which is in Normandy), Étretat, the D-day landing beaches, Cherbourg, and Mont-Saint-Michel. Many people from the States mention "Normandy" meaning the D-day landing area. for that area, I recommend Bayeux as a central town with hotels, dining, half-timbered buildings, easy access to the beaches, etc. But if you clarify what you want to see and visit, you may get other recommendations.