Thanks for that. I registered with Worldpoints. It would cost ST£15 to buy two single tickets but they have to be collected on the day at the station. I'd prefer to have the ticket in my paw to save time, so I might just buy them from Ryanair. Many thanks, all the same.
Depending on your plans, you might just be better off bypassing the Stansted Express desks altogether, going down into the railway station and getting ordinary Travelcards, which are often heavily discounted and give you unlimited tube and bus use in the greater London area for the time period chosen (see p. 6 of 30 in [broken link removed] .pdf file).