You would have to notify a CE for one of the reasons stated in clause 60.1 and subject to any time-bar if you became aware of the delay more than 8 weeks ago (unless there was an instruction).
When you come to the quotation stage, you will build-up the Defined Cost based on current costs, adding risk allowances as Steve Brown correctly mentioned.
So in short, I would suggest that you have a case, but you need to follow the process carefully as set out in your contract - read carefully Section 6 - Compensation Events, additional sub-clauses under clauses 11, 60, 63 and 65 for Option B, and the Shorter Schedule of Cost Components (SSCC).
All the above, assuming that there are no relevant amendments in your contract, by way of z-clauses or otherwise. If you are not familiar with these processes, I would strongly suggest that you seek professional advice.