If you haven’t used Gagfare yet then do take a look.
Their unique proposition is that you can book up to a year in advance and hold the ticket until the ticketing deadline with charges for this as low as US$2 for up to 9 people.
Its ideal for when you want to make plans but not be locked in. For example Xmas holidays, Rugby World Cup, Conferences etc.
Not all flights have this facility so you do have to dig around a bit but definitely a feature we like