I work for a bus company..

The best thing to do is contact the local council, and find out if its a council subsidised service, if it is, you can complain to the council and they'll pass the complaint on to the company running the service (and trust me.. They go radge!)
If it's not a council subsidised service, either contact the bus company themselves and ask to speak to someone in a managerial position (although from your post, I'm guessing you don't know which company the fella was driving for) OR failing that, I think there might be a complaints form to fill in on the Department of Transport website.. Or VOSA.

Hope this is of help

Emma.