Firstly you need to satisfy yourself that the matter is a CE under the contract. Clause 60.1(2) provides that there is a CE if access is not allowed by the access date and the date shown on the Accepted Programme.
Should the matter be a CE, then the question to ask is what the Define Cost would have been had the CE not occurred v the Define Cost including the CE.
If it had been possible (had access been given) for the labour to have been used elsewhere having finished that element of the work then there is additional cost that the contractor should be compensated for (together with any delay).
The matter is not whether it is disallowed cost but whether there should be a target (Prices) adjustment.
Should the matter be a CE, then the question to ask is what the Define Cost would have been had the CE not occurred v the Define Cost including the CE.
If it had been possible (had access been given) for the labour to have been used elsewhere having finished that element of the work then there is additional cost that the contractor should be compensated for (together with any delay).
The matter is not whether it is disallowed cost but whether there should be a target (Prices) adjustment.