I have managed to source the solution.

This can be changed in “Supplier for Purchase Part”. Go to Suppliers Part No. tab & enter the new or revised number

Hi Chris, 

I can verify that is the correct solution to change Manfacturer Part No from Supplier for Purchase Part.

Additionally, if the actual part number or serial number is modified, this can be performed through the Rename Serial workflow executed from the “Part Serial” page. 

IFS Cloud Documentation - Rename Serial

Best Regards,
Sayeef