I bought it from another retailer (Game - who is sort've the equivalent to GameStop in USA if you're there?). I've already contacted them and they said they don't have any other codes listed for me other than the one I've already been sent. I've seen a lot of other people have the same problem as me?

Retailers distribute codes so you'd have to put your foot down with Game. Since you purchased through Game, they're supposed to give you your codes.

So the retailers definitely give out the codes? Are they separate to the game code or with it?

The codes would have been separate from the game, not in the game box.

I ordered a digital version of the game - so the game code was emailed to me first anyway (the day before release on the 19/09). I contacted GAME and they said they only had the one code on their system though for me.

When you entered the code, what purchased item came up? Just "Destiny - The Collection" and not the Destiny - The Collection preorder bundle? If so, then you were given a normal code instead of a preorder bundle code, and that still needs to be resolved with GAME. Sadly, Bungie does nothing, code-wise, and won't give you one, even if you can prove that you were supposed to get one; that's entirely on GAME. Good luck. P.S. - One thing to try, check your downloads and ownership thing on PSN (I've no clue how, as I use Xbox), if it shows you own the preorder bundle items, you may just need to restore your license and go into the game's information hub thing to see if there's a way to manually download the pre-order things. If it doesn't say you own the pre-order things, then it's back to being on GAME.

It doesn't really matter much. Bungie doesn't issue codes, so if Game says they only have one code for you, then you may be out of luck.