LONDON, Sept 6 (Reuters) - British new car registrations in August fell 22% year on year, preliminary industry data showed on Monday, with the sector still battling pandemic-related supply difficulties. Over the first eight months of the year the market is up about 20% from 2020, the Society of Motor Manufacturers and Traders (SMMT) said, though numbers remain below pre-pandemic levels as the sector contends with semiconductor chip shortages caused by the coronavirus crisis. Demand is normally quiet in August because many buyers wait until the licence plate series is updated in September, one of the two annual updates. The SMMT will publish final August figures at 0800 GMT on Monday. (Reporting by Alistair Smout Editing by David Goodman)