Moving our household items to UK after 2 years (London)

Hi, we have been in the UK for 2.5 years and since we were not sure if we were staying we left our household goods in storage in Chicago. We now are deciding to stay and are bringing our goods across but I found out that you are supposed to bring them over in the first 12 months. I am worried I am going to have to pay tax on items that are over 12 years old. Anybody know how this works? Our stuff is already on its way.