Wessex would stress that just because you have the right classification on your driving licence, this doesn’t mean you should drive a Minibus. Just because you can, doesn’t mean you should! We would always recommend training, and experience is critical even when you have the right licence. This is the most important factor in whether you should drive 17 people in a bus.
If you look at things from a purely licence perspective, if you passed your driving licence before 1st January 1997, you will likely have a D1 on your licence. This is essentially grandfather rights and allows you to drive a 17 seater minibus as long as it’s not for hire or reward.
However, please please consider whether you should. If you have a D1 but haven’t driven a bus for 20 years, you’ll likely benefit from additional training.