If it has a reverse gear you definately do need a car licence. You used to be able to drive them on a motorbike licence if reverse was 'blocked, but I think the rules might have been changed. Perhaps someone else can give a definitive answer.
You can still drive a three wheeler on a motorbike licence, including a Robin IF you have B1 entitlement on your licence. If you got your motorbike licence before October 2000 you will already have B1.