We are working under a JCT SBC with Quants. The client wishes to omit works. The materials were ordered before the instruction was given and it has been agreed that payment will be made and ownership transferred to the client for those materials, however other associated works i.e. supply, install, test and commissioning, were priced as a lump sum. Some of these works were undertaken and some were not. We are trying to establish the value of each constituent part for the purposes of valuing the omission and have asked the contractor to provide a breakdown of the lump sum. The contractor has not provided the breakdown but offered a saving which we consider to be very low. We have undertaken our own assessment which the contractor disagrees with. I understand that were the value is not agreed between the employer or contractor than the valuation is undertaken by the QS. Might anyone be able to offer any advice on the best way to proceed to avoid dispute resolution.