That's great. I'll be in touch about the IPN when I get the go ahead.
One last question though: does a user HAVE to return to the website where the purchase was made for the IPN to work properly?
I ask because at the moment, if a user does not return to the website where they booked their ticket, the IPN appears to fail and the booking does not show as confirmed. We would have to make the IPN work as soon as payment is made rather than the user returning to the site.