I haven't seen the film and can't imagine Connery being Barley

I think you should watch the film and make your final judgment after that time. Connery is a brilliant actor and does not get the credit he deserves. People tend to think he's only good for playing the tough, sure-of-themselves characters and, while he has made a career playing a lot of those kinds of roles, he was still capable of surprising everyone with a beautiful, deeper performance. I think this film contains one of Connery's best efforts.

Also check out The Hill (1965).

I'm rereading the novel right now as well. I've seen this movie countless times and, yes, Connery is brilliant in his portrayal of Barley. It was a departure from his normal characters, and he does a great job. However, I still think he's too old for the part. Great acting--a truly great performance--but he should have dyed his hair and shaved the goatee. That's the only flaw. Otherwise, they should have cast someone else.

It's a great novel, isn't it?

The only second chance you get is to make the same mistake twice. - David Mamet

Well, I finally got to see the film.

Yes, Connery does a great job. But I think his character of Barley is not the same character as the novel. His film portrayal does work, maybe the subtle inconsistencies in the novel character wouldn't work in a film. Maybe they'd work in a mini-series. For a film the more straight forward and consistent character, which Connery is a master of creating, works.

But now I have another complaint. Although it was good to not have a narrator, why did they have to get rid of Harry altogether? If he's there he is so minor I couldn't never place him.

I had the same misgivings going in, having also read the novel first. But Connery never really worked for me. His confession of love to Katya was all wrong. Barley was a musical drunk, an idealist and dreamer. I'm not sure even the book fully fleshed him out. Connery did his best, but I couldn't help but feeling a character actor would have been more right for the role.

..You've read the book, but have not seen the film.
I have not read the book (but am a LeCarre fan..). I have seen the superb film.
Connery's is a standout performance, matching the tremendous cast assembled and that is saying an awful lot.
If you don't want to take a risk on the film because of your preconceived Connery image (James Bond era..) that is unfortunate. Connery indeed matches a certain mix of hesitation, enthusiasm, cynicism and loyalty, though I can't say if that is 'LeCarre's mixture.'
You're missing a tremendous lot.
See the film. For my money, this Connery performance should have been Oscar nominated. It outdistances, for example, his acting in 'The Hunt for Red October'.

Hugh Grant? It would be Notting Hill House with Hugh fluttering his eyelashes all over the place. Nobody bookkeeper becoming a spy and falling in love.