6 months.
'Base training', i.e. the aircraft training required prior to issue of the rating, is an integral part of the type rating training course and usually includes the pre flight inspection that cannot be completed on a simulator.
JAR-FCL 1.240(b)(2) states "Each applicable item in the appropriate skill test shall be satisfactorily completed within the six months immediately preceding the date of receipt of the application for the rating." so you must complete all parts of the LST, including the base training, within 6 months of the Authority receiving application for the rating.