After some EXTREME Google-fu. I have found the following.
"Luke: Thank you for contacting EA support, my name is Luke, how can I help you today?
you: hi
you: i've got a question about bf4 preorder
Luke: Ok what is your question?
you: i saw on battlelog that info: "Pre-order Battlefield 4 now and get a Premium expansion pack at no additional charge."
you: what does it mean?
you: if I preorder bf4, I will recieve any DLC when it's out?
you: like premium in bf3?
Luke: That means you will receive the first DLC with the game at no extra charge, so like if you pre-ordered Battlefield 3 you received Back to Karkand, you will receive the first DLC for Battlefield 4
you: only the first dlc?
Luke: Yes just the first DLC.
you: ok, that's everything
you: thank you
Luke: No problem, thanks for contacting EA support"
This can be found here:
http://battlelog.battlefield.com/bf3/en/forum/threadview/2832654348483926309/
So it's the game, plus the very first dlc they release by the looks of it. Still a good deal though.
RJ - If the price is cheaper at the time of release, will OcUK refund the difference, or is the price the price?
disclaimer - "you" in the chat log and his terrible typing is not me