Steven - when ever there is a compensation event this should be assessed in terms of its impact to the project based on the last Accepted Programme. This will be in terms of both time and cost. Whilst you are obliged to mitagate any delays where ever possible, you are not obliged to “accelerate” any works such that you incur additional cost and/or risk to you the contractor. The intent of CE’s are that you do not lose out from having to do additional works but equally do not take advantage of the Employers problems by making significantly more money off teh back of them. You are intended to recover the likely cost you will incur plus your fee - no more and no less.
To have the Employer add significant additional works and expect a fixed date to be maintained at all cost is not the intent of the contract. And if you do view that you can maintain the date they are looking for, then at the very least you should have the chance to price all associated risk accordingly within that quotation. If a compensation event pushes out planned Completion compared to that on the last Accepted Programme then clause 63.3 states that Completion Date moves out by the same amount once that compensation event becomes implemented.
I am sure that this will not be the last Employer that you ever come across that expects a Contractor to maintain a specific end date no matter what, but the contract should be there to protect you (but do check the Z clauses as there may be aspects that have been changed accordingly!).