road rallys

Well going to you're local motor club is a start, also have you been out to watch or Marshall on sone events, marshalling will give you an insight into how the work and what goes on during the event. You could start by doing passage controls as these only require you to sign the competitors time card to confirm they have been on the correct route, its a good starting point

Sounds like a very active club there, so it would be good start to join them,
Autotests are a good point to start I've done a few of them, can be a good point to learn some car control but you won't get as much fun as doing a road rally or even a stage event but they are good cheap astringent point.
Shame your dads not interested in navigating for you, but if you join the motor club and go to the meetings I'm sure you will find some one that would be willing to sit in with you, it can be good to maybe get one of mates to try his hand and navigating and learn together as this can be a bit of fun and neither of you will have any great expectations of the others ability