I have received a message from UCL that their LLM programme will begin with online learning. Does anyone know if such online teaching arrangement will be for the whole year? Or is face-to-face teaching possible depending on the COVID-19 situation?

The message:
How your modules will be taught

All the learning activity for the core content of your modules will take place online – including lectures, tutorials (where applicable), seminars and assessments. A limited amount of face-to-face educational activity will be offered on campus in the form of research workshops (with alternative activities for those of you unable to join us in person). More information on these workshops will be provided before the start of term.

Like most schools they probably can't plan out that far. Things have been changing so quickly that they most likely can't make that kind of call at this point.

But you can always ask them, maybe they have a plan to bring back face-to-face classes. Doesn't seem that way based on the info provided here, though.