Nothing beats a night at the theatre, opera or ballet in London: the picturesque ride to Darlo by car or bus; the happy match-goers on your swift and punctual train; the thrill of the crowds at King's Cross, and your swaying journey on the Underground; the satisfying cost of it all...
On reflection, why not just go to The Station in Richmond? There you can enjoy a relaxed dinner before the show, then watch the main event in all its wide-screen glory, before heading home to your own comfortable bed - and all for a small fraction of the cost.
The Station Cinema has regular screenings, both live and recorded, of performances from the National Theatre (Othello, The Crucible), the Royal Opera (The Barber of Seville, Turandot) and the Royal Ballet (Sleeping Beauty, Cinderella) at Covent Garden. You'll enjoy the best view of the action, the best artists in the world, and the best price.
Book at the Station Cinema's website. It's a shame you'll miss that hen party in LNER's 'quiet' carriage, but hey.