You don't need an instructor rating to teach aerobatics. According to the ANO Article 36, an instructor rating is required only to give instruction leading to the issue of a licence, rating or other qualification in the licence and there is no such thing as an aerobatics rating.
The privileges of a JAA FI rating, as detailed in JAR-FCL 1.330, do not include the teaching of aerobatics and so the 'No Aerobatics' restriction placed on the rating by the CAA is entirely meaningless - it's a bit like putting a 'No HGVs' restriction on a motorcycle licence.