Implementing a compensation event has nothing to do with carrying out additional works; it merely finalises the effect upon the prices and the completion date. Clause 14.3 allows the project manager to instruct a change to the works information, clause 27.3 requires a contractor to obey such instruction and clause 61.1 requires the contractor to put such instruction into effect immediately. Further clause 63.7 requires that compensation events are assessed assuming that the contractor acts promptly and competently.
The contractor cannot wait around until the compensation event has been agreed or assessed. The contract requires that the contractor gets on with it, whether that means putting the instruction into effect or dealing with the compensation event if it is one does not arise from an instruction. If the contractor fails to do so, the compensation event will be assessed assuming that it did - and the contractor may not recover all the time and more that was down to its failure to act.