Yes you are obliged to follow the instruction, but if you believe this event to be a compensation event then you can notify that fact explaining why you strongly believe it is one (knowing you know they don't think it is one). If they still don't agree then you could go to adjudication (and normally the threat of going is enough for them to change their mind if you are right).
The fact you did not price for this is irrelevant - it is whether you SHOULD have priced i.e. was it in the original Works Information. If they are instructing something that was already part of the Works Information then this will not be a CE.
The fact you did not price for this is irrelevant - it is whether you SHOULD have priced i.e. was it in the original Works Information. If they are instructing something that was already part of the Works Information then this will not be a CE.