It is better to make any proposal to settle at an FDR on a without prejudice basis rather than as an open offer. Courts have a strong tendency to 'split the difference'.
Say there is £100K to argue about. You make a without prejudice offer of a 60/40 split in your spouse's favour. It is rejected and it then goes to a final hearing. At that final hearing you will be free to argue that the split should be 50/50. If you were unwise enough to make your 60/40 offer as an open offer then you would find at a final hearing your ex would be arguing for, say, a 70/30 split. Your 60/40 open offer would be taken as a base line. If a court then split the difference it could order, say, a 65/35 split. You could have avoided that situation by making your 60/40 offer on a without prejudice basis.
