Provisional sums should not be used with NEC. The Works Information should clearly set out what the Contractor is to provide.
If the items were not in the original Works Information then they should be instructed under 14.3 and treated as a CE under 60.1(1). The CE would then be evaluated on Defined Cost + Fee.
If the items were included in the Works Information then you may have an argument that there is a mistake in the BoQ that needs to be correct in accordance with 60.6 and this would be a CE. The CE would then be evaluated on Defined Cost + Fee
If the items were not in the original Works Information then they should be instructed under 14.3 and treated as a CE under 60.1(1). The CE would then be evaluated on Defined Cost + Fee.
If the items were included in the Works Information then you may have an argument that there is a mistake in the BoQ that needs to be correct in accordance with 60.6 and this would be a CE. The CE would then be evaluated on Defined Cost + Fee