Well. I don't want to worry you Smurfchops but my wife and I went from Lymington to Yarmouth in November about four years ago. I don't know what the windspeed was but it was really blowing a gale. The blunt bow of the WightLink ferry kept slamming into the waves and almost stopping dead each time. The wind was blowing from the side and the ferry was heeling over so far I kept thinking it might capsize! In the end, I left my wife in the warmth of the rolling lounge and spent the crossing on the open deck! I ended up windswept, frozen and soaked but I reckoned that if the ferry did roll over at least I would go into the water and wouldn't be trapped inside! It sounds daft now but it was frightening at the time.
I hope you have a good crossing but be prepared for the weather to be dodgy at this time of year.