The tympanum above the West door to Westminster Cathedral, London   Performers from six European countries will come together in Westminster Cathedral on 20th November, to perform the UK premiere of Jean Guillou's spectacular La Révolte des Orgues, a 25-minute piece for percussion, and no fewer than nine organs.  Some of the musicians have played La Révolte before, but not all, and rehearsal time is limited, starting on 17th November, when Viscount Organs will install seven digital instruments, to add to the Cathedral's Apse and Grand pipe organs. 'The set up will start after Mass on…