There are moves afoot for EASA to introduce aerobatic ratings, but I'm not sure how far along that has moved.
Assuming that the great EASA gravy train is not derailed in the meantime, the aerobatic rating is due to become law on 8 April 2012. You will be able to gain the rating (provided that you have at least 40 hours flight time since licence issue) by completing a 5 hour course at an approved training organisation.
There is, at present, no provision in Part-FCL for credits to be awarded for previous aerobatic experience.