Thanks Nathan, the update as partially solved the issue. However, now the successful recording of payments only works if you were logged in as a member. Our events do not require you to be a member and none members attempting to book on he paid events don't get captured via the events record. However, we get the paypal direct emails to say we have been paid. the none payment bookings work fine logged in or out.
Im not sure if the changing the CURL setting as effect also.