Finally got it sorted!
Right, called an EA adviser and she was helpful, gave me a new code, however it didn't unlock the weapons in game. So I called again and this time a chap answered. I told him the problem and he said "is your case number xxxxxxxxx?" I said yes and he said "ok don't look at it too long, the banana will rot"...Awkward silence for about 10 seconds and then I said "what?", he said "It was just a joke, I did it while your details loaded up in the system", another 10 seconds of awkwardness passed then I carried on telling him about the problem. So he asked where I bought the game from and I told him Amazon, it was the Limited edition one. So he went on amazon and told started reading the description and noticed it didn't say anything about the physical warfare pack (weapons pack), just about the back to karkand pack. He said it must be an UK thing, that amazon didn't include physical warfare pack, just gamestore included it in their preorders. He said he didn't mind giving me the physical warfare pack code anyway, so he sent me an email with the activation code and a 20% off next origin purchase code. He must have felt bad about the awkward joke hahaha!
Went in-game while he was still on the phone and weapons finally showed up, so all good now! I told him he was the first actually helpful EA adviser I've dealt with, and if I had any future problems I'd like him on the end of the line, he laughed and thanked me. Nice chap.
Anyway, finally sorted. If anyone has any problems with the code ring 08702432435 and just hold, it'll eventually put you through to someone. I told him that lots of people were having problems with the activation code, and he said yeah, it's a known problem and he knows exactly what it is, but didn't share details. EA for ya, full of bugs!