I have puchased a few bridge packs and I can't seem to use them on this ship. I purchase, save and then when I go back to my ship its still the same old bridge. Am I doing something wrong or is it a bug. I used to fly an assault cruiser and had no problem using them.

Very frustrating as I paid for these would like to use them.

You need to change them at the fleetyard i ship customization, their should be a drop down near the top left that'll allow you to select a bridge, and an interior layout for the other decks.

Edit: If you're saving in the ship customizer, you're saving the configuration but not applying it, you have to click "buy" or whatever the option is further to the right.