I wish people (especially those who took the spouse route) would stop giving incorrect information about fiancee visas. You do not need to have evidence of any bookings, and even a provisional date might be difficult if you don't know when the visa will be granted.
The ECOs know it is difficult if not impossible to make any real arrangemens for a wedding in the UK until both the bride and groom are actually in the UK. Also you could have the biggest wedding provisionally booked, but it doesn't actually mean you are going to get married.