As a rule I swerve new operas and plays. They are not always bad but that’s the probability. Conversely a new ballet is worth the detour but it’s less of an investment as it’s shorter.
I saw The Rocky Horror Show at a theatre in the King’s Road (possibly The Royal Court) in the 1970s and was taken by surprise when the audience were mostly in costume and participated in the show – I remember lots of rice being chucked in a wedding scene.
Crowded bars, warm white wine, poor sight lines and uncomfy seats sum up an expensive visit to a West End theatre in the past. I used to game the system by ordering dry cider and ice for the interval.