I know your mind is probably set now on not importing the 550i but - another thing to consider is this:
A left hand drive 550i will be worth next to nothing come resale time in Ireland - unless you were to export it to europe!
As someone else said 99% of F10's are 520d's due to high road tax and fuel costs in IRL.
Due to recession, very few thirsty cars are finding homes.
Good luck with the move - and dont forget your raincoat