Are costs incurred as a result of a delay to completion caused by the main contractor recoverable under Clause X18.1 for indirect or consequential loss?
Clause X7 is set at £0 so the Employer is seeking to recover costs for their consultants fees, rent of temporary accommodation, and a cancellation fee for Statutory Undertakers work (BT) through X18.1
Secondary Option X18 states what the limitation is on various liabilities, such as indirect or consequential loss, and is not a contract mechanism for recovery, which is dealt with elsewhere in the conditions of contract.
As you have Secondary Option X7 then associated delay damages are £0, as stated in the Contract Data, which is what the Employer / Client can recover.
There may be an issue of Losses, however under clause 83 (NEC3) but these would have to align with the stated description.
It looks to me like somebody has made a mistake by entering ‘£0’ against X7 and there is an attempt to circumvent this by looking at avenues of recovery for unliquidated damages, although as Secondary Option X7 has been selected and the amount set, then that is what is recoverable.