The only legal way to watch NBA games for free is by watching betting sites' live streams. Many UK-licensed bookies offer NBA live streams on their homepage. For example, Coral's and Betfred's NBA live streams offer thousands of hours of sports free of charge every week.
Typically you can start watching live streams with the following manners:
Visit a betting site that provides NBA live streams.
Make a new account or sign in
Select "live streams."
Place your bets and watch your favourite basketball game!