Mike

I read with great interest your inquiry regarding transatlantic flight

I made the trip several years ago in the 310 I had at the time.

• Insurance is the biggest preflight issues. Some countries require it. I was never asked to show it (or anything else for that matter), but you should look into that issue now.
• The trip is all about weather.  The icing level never gets above 5,000 ft. even in July. The weather can be nasty and turn quickly. The nearest alternate can and will be 200-300 or more miles away.
• At one time there were  “issues” around experimental aircraft in some countries and IFR flights. You should look into this issue now also.
• Allocate a lot more time than you think you will need. You could be stuck somewhere for days. Plan to make the most of it. Don’t get into a situation where you feel any pressure to launch on a leg. We had an understanding that if either one of us didn’t fell right about a leg for any reason, we would wait until it felt good. It never happened, but we were prepared

Recommendations

• Look for a transatlantic "Ground School" I used Ed Carlson. I don't know whether he is still doing this.  Most of the rules, regulations and “how to information” you could get off the Web.  However people like Ed provide absolutely invaluable information about FBO’s (handlers), hotel/B&B, telephone numbers, weather trends etc. And last but not least answer all the questions that come up about what is important, and what is not. 
• Talk to every ferry pilot you find along way, they know the drill and what looks good and what doesn't. A night “on the town” in Goose Bay with a couple of ferry pilots is something you won't forget!
• Get the local (destination) telephone number for weather for the critical legs  (Greenland, Iceland and Goose bay in that order) and call them just before you leave.  It might take a bit of talking, but you can usually get a pretty knowledgeable opinion. These folks know the local weather patterns and how they change
• Talk to the airline guys on the assigned frequency. There’s always someone there, and they can get weather for you. In addition ask them to look out the window and tell you what they see.  They can see a long way!
• Construct a simple Excel spreadsheet with the required information for position reports because you will have to do lot of them in the right sequence. Also fill out and make many copies of the  ICAO flight plan. It is a real pain. But most of the info doesn’t change. You get a very positive response when you hand someone a form that is legible.
• Avoid temporary fuel tanks if at all possible. If you go Greenland/Iceland you might not need one. Get the regs and run the numbers now. OTOH, if you are in the construction phase consider permanently plumbing in lines for a removable aux tank. I am.
• Get a good moving map. The best bet is a PC based MM since you can use it for flight planning and Enroute Most of the air space in Europe, with the exception of central France, is controlled and many of the fixes are ADF’s. In addition, use a MM to create your own GPS overlay for places like Narsarsuaq. Narsarsuaq is the most difficult and expensive place. Beware of arriving or departing when the airport is not open. The cost is staggering. Also, Jet A is ~1/3 the cost of 100LL. The approach must be the wildest one in the world. It is (or at least was) an ADF approach with the IAF at 6000 feet over the airport. Have a look at http://iserit.greennet.gl/bgbw/ if you haven’t already. Returning, you need 13,000 or more over the southern tip of the polar ice cap, and most people hold that altitude until you can see Narsarsuaq, which means you start your approach at 13,000 overhead. The ultimate slam dunk approach
• Be prepared for some pretty hefty bills. The 310 was just over 5000 lbs at gross, which ups the anti. I got bills for months that had ridiculous cost algorithms. Bureaucracy gone amok. People in the user fee system have to justify their existence so they make up ridiculous rules. I could have papered the floor of my hanger and probably the 310 too. I offered to do this for the AOPA so they could show folks what user fees are all about (one picture is worth a thousand words) but they ignored me

Mike, I hope all of this hasn’t discouraged you, it is an incredible experience for many reasons, not the least of which will be the other pilots you meet doing the same thing.

Europe is actually very small, and if it weren’t for the airspace and bureaucracy would be easy to get around. I had been going to Europe for 25 years on business but never got to the Channel Islands, the Isle of Mann, Le Mans (the airport is next to the track), Donegal  or circled Omaha beach at under 1000 ft. I did in the 310 and will again in my IVP.

We had great weather, stopped in 9 countries, flew 18 legs in 12 days, got as far south as Geneva all in 20 days. We had tail winds both ways. I have never complained about head winds since then, and never will again!

Hope this helps

Regards