Possible but certainly uncomfortable, and the harbour will be uncomfortable too. Don't try at low water - you may touch on the bottom of the swells. The swell is more important than the wind. Unfortunately, with a W or SW wind, once you line up, you're probably committed. And watch for cross tides.
I remember it at the time. I ain't been to Fecamp but was thinking about it for next w/e. However that was one story that makes me treat it with respect. From what I recall, it was only due to the bravery of a french swimmer that there was no loss of life?
Dodgy in winds from west-north ,so 'ave a nice big engine for the confused seas sloshing through the breakwaters,better still keep the main up until you are actually inside and time it for HW -1. Force 6? Not for me thanks.
...but it doesn't have a Benedictine distillery! Actually I was going to suggest the same thing - Dieppe is the usual escape route for me when the weather's too lumpy for Fecamp (which in my book would certainly be F6+). There's a vicious tidal set at Fecamp entrance (particularly to the north if I remember right), so you have to keep very one-sided on the entrance to avoid being swept into the wall, which a big swell helps not at all.
The going in was bad enough (only because we managed to be 3 boats abreast at the entrance, all under sail, in the F9), but coming out was worse. The little engine could only make about 0.5 knot, and the propellor came out of the water on each wave! However, Fecamp remains a favourite destination.