Dave & Chris,
A noble enterprise gentlemen, but please take the advice of other PPruners re the suitability of the Comanche 180. Seagull also has a deal of Comanche 180 time and can verify their advice and concerns. The 180 might fly OK in the UK, but you are going to have to carry a very big load out of a lot of hot places and fly at very high altitudes where you will need the performance the 180 does not have.
Now the PA24-260 is a difference beast. Read Sheila Scott's book, "I must fly". She was dead set on a Comanche 400 for her round the world trip, but could only get hold of a 260, which annoyed her somewhat. As it turned out the 260 was the best choice and absolutely blitzed around the world with a minimum of fuss. The only trouble she had was with bureaucracy. Horses for courses.