You don't need to worry - we do not allow this to happen. If your standing order has been set up correctly in advance of the First Payment Date then you can rest assured that your place on that event will be confirmed when your initial payment is received.
When we have no capacity restrictions on events we try to open bookings as early as possible to give attendees plenty of time to plan their booking. This may mean that it is possible to book a confirmed place on an event by paying online before the First Payment Date of the associated OUPS PayPlan.
However if we are restricted by the size of a venue then we will not open the event for online booking until the First Payment Date, to ensure that all attendees have equal opportunities to book irrespective of the payment method they choose to use.