In answer to your question about taking a single turbo prop across the Atlantic in Jan / Feb - if you haven't done a crossing before as a minimum take a safety pilot with you who has. I took my PC12 to Canada from Europe a couple of years ago in the summer (August) going UK - Iceland - Greenland (Narsarsuaq) - Goose Bay / Canada, and in height of summer it was a 'challenging' trip, then this year bought a CJ back the other way in Jan,and scared the daylights out of me, weather can change quickly. You will need survival suits, liferafts, HF radio - Far North Aviation in Wick hire all that stuff, and you can drop it in Goose Bay. All other planning requirements can be found in Jepps manuals. In summarry taking a single across in winter months - you need to know what you are doing and have done it before - good luck.