P310 4-Tel 310 Fri 23 Dec C4 00:53:22    BEAT THAT EINSTEIN   Tonight, 20.00-20.30  PREVIEW Hosted by comedian and Whose  Line Is It Anyway? pianist Richard Vranch PhD, this is the final programmj of the series which challenge the pzblic to solve problems. A piano appears again this week, this time stranded on an island in the middle of a lake near Southampton. Using only a bottle of gas, a large roll of cling films and some copper- piping, it must bj hauled ashore. Another team must paint the Brighton seafront with paints made themselves. Subtitles 888 NICAM stereo