LONDON, Jan 2 (Reuters) - Aldi UK, the British arm of the German supermarket chain, said on Tuesday its sales increased 8% in the four weeks to Dec. 24 to top 1.5 billion pounds ($1.91 billion) for the first time. ($1 = 0.7858 pounds) (Reporting by Paul Sandle; Editing by Sachin Ravikumar)