Thank you Bill - I was able to enjoy the performance after all - and what a performance it was!!!
Just a warning to others leaving tickets at the new (possibly temporary) Box Office - the staff don't seem to be familiar with the usual practice of people leaving tickets for others to collect. I wasted ages waiting for it to appear and when it didn't, this lead to me being cross questioned about its origins. Although I prevaricated, there was inferred disapproval. Fortunately, after contacting the seller through the website, he telephoned me and spoke to the member of staff who reissued the ticket with ill-concealed bad humour. Speaking to the seller, I know it was left for me as I have bought from the him before with no problems - its a mystery where it ended up and why it wasn't brought to the Box Office 90 minutes before the performance as usual. This might be a problem for others intending to use the same method to leave resold tickets for collection. It would be a good idea to obtain contact details of the seller in case this happens again.