14.4 update taking ages

Hi, I've had to replace my broken iphone 7 with another 7 as my contract isn't up until May. Fabulous phone, set up went fine. I am trying to install 14.4 update on it and it has taken ages. 18 minutes to download and it's been sitting at preparing update for ages now. Is this a massive update or has anyone else had problems with this? Help :)

Updated to add that the button for the updates is still rotating.