having imported aircraft my advice would be to get ALL the work done in the USA new engines from the maker and not some OH shop that will only honor the waranty if the engines are returned to the shop ,also overhaul the props ,do ALL the AD,s and get the radio fit the way you want it , this will all cost you about half the european price then when it is ready to come over you MUST i will repeat that MUST get an export C of A or puting it on the british register will be very costly if not imposable.
Keep away from maintenance outfits on the coasts as some who have had a lot of business with the brits know to much about european prices and load there prices acordingly.
and why put it in a box after a few hours of shakedown flying tha atlantic should not be to much of a problem for a good ferry pilot.