are you sure you're flying via terminal 3?
I think that the delta in terminal 3 is for domestic flights only.
if you're flying in from the UK into JFK, then i would think you'll arrive in terminal 4.
I usually arrive in terminal 4 (the international terminal) and then have to drag my body over to terminal 3 to get on a domestic delta flight down to MCO ...
as i recall, terminal 3 has a food court....terminal 4 has some stuff, but nothing to write home about.....