I have a 50/42 chainring combination on my bike, for which I ordered a
regular Campagnolo Chorus front derailer from mail order. However, I
received a Campagnolo Record CT front derailer, complete with carbon
fibre and titanium.

Is there a problem with using a CT front derailer, as my outer
chainring has just 50 teeth, like your usual compact cranks? What
difference does it make if my smaller chainring is bigger than what is
usually found on compact cranks?

Obviously I can return this and get what I actually ordered, but you
always have second thoughts when you get more than what you paid for.

-as