Hi Giles,
I know what you are going through… I am new at video editing and just bought FCP X and a Panosonic HMC80, same line of camera as you. I too ran into the same issue trying to import MTS files. Turns out there is a download from Panosonic that I tried which works for me: https://eww.pass.panasonic.co.jp/pro-av/support/desk/e/download.htm#avccamvmac
By using this now I just pop in the SD card from the camera and click ‘import from camera’. FCP X shows me the MTS clips and I can pick what I want and import them.
Good luck and let me know if you have a problem.
