Out For A Trial At Silverstone -- After mechanics had worked day and night to eliminate cerebration snags, Britain's 200,000 pound B.R.M. racing car was ***** for its first great test - the International Trophy race against the best cars in the world - at Silverstone Northants., today (Saturday). The car was flown from its testing ground at Folkington this morning, just in time to be admitted for the day's programme. But first the stewards requested a three-lap high speed test, because the B.R.M