Thanks Lab183 for your reply.
I should say that I thought Sean was wasted in the Martian simply because he is too fine an actor to be thrown away on small roles that require little of him. It wasn't his fault, it was just that his part in the film was so under-written that there was nothing to do with but don the argyll slipover and look like a nice guy. I wish that he would pick up something meatier than this. I can't help feeling that he's getting ready for retirement and no longer cares much what he does. He's entered the big league of bit parts - a sort of 'cult' actor who everyone enjoys spotting on screen but who seems to have dropped off the list of actors who are capable of carrying a whole film (or indeed even a properly well-written character cameo).
His contemporaries (Ken Branagh, Colin Firth, Stephen Rea etc) are all suddenly landing the kind of interesting stage and screen character roles that are great for middle age. Where is Sean among them?
This to me is an really a great pity.