It's very normal to want your child to do well.
I guess he's got no impetus to grow beyond where he is. He's comfortable.
The thing is, I look back and think I could have gone to Oxbridge if I'd know it existed.
have you ever been OP?
Sometimes we need to visualise ourselves in a place to understand that it could be for us. So if you want him to aim higher, book a day trip or a weekend to Cambridge or Oxford and see what he thinks. Don't mention uni but you could have a tour just for fun perhaps or go punting. He'll soak up the atmosphere etc.
It may put him off completely which is fine. But I wish someone had taken me on a day trip to one of these places and made me realise that it was a possibilty for me. You don't know what you don't know.
But in the end, if he's happy and getting on well in life otherwise, that's good enough. Maybe let him find his own path.
but yes, the key to ambition is exposure and it sounds like at the moment he's not exposed to anything much to light his fire.
Working hard comes from intrinsic or extrinsic motivation. Have a google.
You want him to feel inspired to work hard, not work work because he's living in fear of not being good enough. So how do you inspire? Take him places, expose him to new ideas and thinking...