It is difficult to provide a direct answer as you say the contract has been amended although it is not clear exactly what has been amended.
The Contract Data Part 1 should state what main option is used and the definition of Defined Cost should state whether you are to use the Schedule of Cost Components (SCC) or the Shorter Schedule of Cost Components (SSCC) to assess Defined Cost.
If the SCC then you would apply the Working Areas overhead charge, if the SSCC then you would apply the percentage for people overheads.
This presumes that no changes have been made to the SCC or SSCC of course.
The Contract Data Part 1 should state what main option is used and the definition of Defined Cost should state whether you are to use the Schedule of Cost Components (SCC) or the Shorter Schedule of Cost Components (SSCC) to assess Defined Cost.
If the SCC then you would apply the Working Areas overhead charge, if the SSCC then you would apply the percentage for people overheads.
This presumes that no changes have been made to the SCC or SSCC of course.