Chaps, here is the reply from IG about the 'Good till' feature I was asking about...
The Good Till/Time in force feature only applies for the Working Order/Order to Open. Daily contract Working Orders will rollover into the next day (at no cost) until they are either triggered, cancelled or reach the deadline you specify. Once the Working Order is filled and becomes a live Order it will only be cancelled or closed in the usual manner for live positions such as either expiring at expiry time, being stopped out or closed by yourself.
The Good Till/Time in force feature only applies for the Working Order/Order to Open. Daily contract Working Orders will rollover into the next day (at no cost) until they are either triggered, cancelled or reach the deadline you specify. Once the Working Order is filled and becomes a live Order it will only be cancelled or closed in the usual manner for live positions such as either expiring at expiry time, being stopped out or closed by yourself.