Yeah for true redundancy you need to pick alternate means of delivery.
In my case I use FTTC primarily, but if it goes down I have 4G as a backup. Completely different techs. I also have the option of VM cable as a third means of delivery.
I am considering a second FTTC line, the main thing holding me back is I might be moving within a few months, so obviously would be bad to commit with that in mind, but if I do get an extra FTTC line then it would be on a different wholesale privder probably talktalk business, but as kitz said I would still be going to the same cabinet and exchange.