Contractor refuses to follow instructions from the Project Manager - what can we do contractually?
You should direct them to clause 27.3 which requires the Contractor to obey instructions, however you haven’t mentioned the nature of the instructions, so the Contractor might be entitled to ignore them if they aren’t in accordance with the contract or given by the right person.
If the instructions are being issued under clause 14.3 i.e. changes to Works Information, if the Contractor does not obey them then how on earth do they ever expect to be able to achieve Completion? Clause 11.2(2) defines Completion as “when the Contractor has done all the work necessary for the Employer to use the works and for Others to do their work”. Failure to achieve Completion on or before the Completion Date would give the Employer the right to recover delay damages under Option X7 (if used).
Ultimately this could be reason for the Employer to terminate the contract, again depending the nature of the instruction, clause 91 sets out the reasons to terminate, the most relevant to this situation are R11 substantially failed to comply with his obligations, or R14 substantially hindered the Employer or Others.