Most of it covered above.
Shortest legs are Stornaway, Reyk., Sonderstrom, Frobisher.
Getting permission for Sonderstrom is a nightmare ( Pentagon and Danish Govmnt.)if you land without permission they just fine you $100 (preprinted on landing invoice!) - worth it if weather not great.
You will need 12k plus altitiude across Greenland so check icing levels.
Check what register the aircraft is on UK or FAA.
Dont rush !! wait for the weather and to hell with anybodies timetable.
By next month weather is better.
GPS is great but dont forget magnetic variation !