I went to my local TRU to get this. Couldn't find any out on the shelves in any of the Lego locations. I asked at Customer Services and because they only had 12 (at the time) they were keeping them in the office and applying the "spend £10, get it free" deal. They were also limiting them to two per customer.
So, try your local store, but make sure you ask if you can't find them
I've heard other stores aren't being quite so strict, so scalpers are just going in and buying them up on mass.
I bought the two 2 battle packs (since I was going to anyway) and therefore got 2 TC-4s free. They therefore had 10 left at the Portsmouth store, after me.