The Vigilant was considered as a Group A aircraft untill JAR-FCL was introduced in July 99. Unfortunately, it then became a TMG under the JAA definitions.
Your best bet is to get the TMG rating added to your licence (grandfather rights if you have 75 hours on them) or by test if you don't.
Then if both your SEP and TMG are valid, you can revalidate by using either in the future.