Although tickets for the three performances (on 10th and 14th October) do not appear to be available on the web site (here's the page I was checking), I've just been able to buy a couple of tickets by phone from the box office on 01789 403492 (that would be +44 1789 403492 from outside the UK).
Do you know if there are any other showings of this play? I saw a banner around Trafalgar Square about an exhibition with Douglas Coupland, but I wasn't sure what it was. Thanks
The exhibition at Trafalgar Square seems to be about Coupland's Canada House work — see his art page (which also suggests he may have an exhibition at the White Cube Gallery, but their web site is well-nigh unusable, and I could find no reference to Coupland there).
The September 10 play was also performed in Calgary in September. The details are about half way down this page. I don't know of any other performances.