Here is a just a quick overview of the different PCV licences available.
Category D - this type of licence allows you to drive a bus with a trailer weighing no more than 750kg. But the bus can have 8 or more passenger seats.
Category D+E - this licence is the same as Category D but with the added perk of being able to drive a bus with a trailer weighing more than 750kg.
Category D1 - this is a minibus licence. With this licence you can drive a vehicle with 16 passengers or less, and a trailer weighing no more than 750kg. Something else to add is that the total length of the vehicle must not exceed 8 metres.
Category D1+E - includes the same entitlement as a D1 licence but you can drive a vehicle with a tailer weighing more than 750kg. However, it's important to remember that when fully loaded the trailer is not permitted to be heavier than the vehicle. Also, the vehicle and trailer combined cannot weigh more than 12000kg.