Re: "a question like "Have you got a pen?" is actually a request to borrow a pen rather than a simple question about whether you happen to be in possession of one."

Not in my house-- we all ways treated such questions literaly--we would reply "yes, i do" and want for the "can I borrow it?" or if they questioner was very slow, look at them surprized and say "Oh, did you want to borrow it? I'm sorry, i thought you were taking a survey!"

if friends called up and asked "is Emily home?" we would reply "Yes"-- "Was there anything else you wanted?"-- and after a moment-- they would realize they had to ask "Can i speak to her?"