Avon doesn't have much to do in Project Avalon. He spends the entire episode on the Liberator, and most of it operating the teleport for the other characters. He does have a couple of good scenes with Vila when Vila doesn't want to teleport to the planet.
"Oh, no, wait a minute, it's cold out there and I'm very susceptible to low temperatures. I've got a weak chest!"
"The rest of you's not very impressive."
Avon gets fed up of Vila's antics and makes this super-grumpy face.
But he smiles when Vila is finally teleported away.
When Federation Interceptors chase the Liberator, and with Blake, Jenna and Vila still on the planet, Avon takes charge. This means we get close-ups of Avon being dramatic.
This could be seen as foreshadowing the events of later seasons of Blakes 7, but it probably isn't really.
Avon makes his biggest contribution to the plot near the end of the episode, when he reprograms the Avalon robot to work for him and Blake instead of for Travis. She is now the Av(al)on robot.
Poor Travis is defeated once again, and he is left ranting to the small pink glowy thing which, in his nuttiness, he has mistaken for Blake.
"If it takes all my life, I will destroy you, Blake."
"I'm not Blake," we don't see the small pink glowy thing say.