It Is GENERALLY intriguing to see lesser-known works by famous dramatists. Sir Alan Ayckbourn has written 79 plays and, inevitably, even some hits will be irregularly staged. Two rarely seen Ayckbourns have just had their first major revivals; both of them darker works from a writer most known for comedy and farce.One reason that Way Upstream, which opened the 2015 Chichester Festival Season, has mainly remained in the archive is that its 1982 London premiere at London’s National Theatre, though admired by reviewers, gave nightmares to insurance brokers. As one of Ayckbourn’s trademark experiments with the conventions of theatre, the play replaces the wooden boards of the acting area with more than 65,000 litres of water, on which floats an operational power boat. At the Natio