I done this trip ages ago! when you get to ferry port go straight to the front as bikes are usally first to go on prob be others there aswell,the 24hr crossing is boring, evening entertainment i thought was naff even could say was embarrassing.
Bay of Biscay can be like a mill pond or VERY rough seas (luck really)
Get pissed then you dont notice the ship rolling about and you then walk in straight line lol!
I had no problems with the Spainish car drivers at all and was away for 4-5months,Flash your headlights when you go to overtake its the norm or was.
youll need spare bulbs complete set and i think you now need a small red warning triangle.motorcycle ones are smaller than the big car ones they use.
I also been along the North coast to the Picos de Europa mountains brilliant place went 3 times trail riding in the mountains.Unforgettable!!
Spain is a brillant place to ride and the Spainish like there bikes which makes it a very biker friendly country,unlike this friggin UK. >
You could check out the Spainish tourist web sites for more info on motorcycle regulations or even RAC/AA
Oh and remember they drive on the right which if your not alert you can easily end up riding down the road on the left for a 100 metres before you remember or traffic coming the other way will remind you.
Have a good trip!