Seeing as I live in France, and go home there, thought I'd pitch in!
If you're planning on going to Holland, be prepared for boring roads. I have family there, and it's all FLAT. Very little interesting scenery there. Some like it though... I personally am fonder of Brittany - but seeing as I live there, I'm biased! Beware in France though, "camping sauvage" is frowned upon (I believe it's technically illegal, not sure how hard it's enforced).
If going through France, the police insist you carry ALL documents at ALL times. So, drivers license on you, and V5, insurance, blah de blah, under the seat.
People seem to think that riding on the right will be as hard as driving a car on the right. I disagree, no passenger seat to confuse you! A few hours, and it seemed like second nature to me.
Stena Lines from Hoek Van Holland to Harwich are comfy, but expensive. Not sure how good they are with bikes, though. DFDS Seaways (Dover - Dunkirk) are cheap, don't know about bikes.
If you plan on heading further South, then LD Lines to le Havre are cheap, and I can recommend their bike care too. When I travelled with them on my 125 last July, there were 30 bikes on the boat, and we got a deck to ourselves! If you'd rather have a faster crossing, then Condor Ferries are GREAT. They are pricier, but they are good with bikes - they have custom mounts for them which locks the front wheel. Not bad on comfort, either. The furthest North they sail to is Cherbourg. Just to warn you though, there's no dual carriageway leading to Cherbourg, so it might take a bit longer getting on the bigger roads.
Hope that helps!