There is a formal route for MPL to CPL.
Assuming that you have been issued with a MPL, you will have already completed the type rating and LST, and the base training.
Unless you completed the actual PPL licence items during the MPL course, I dont think you have a PPL as part of this professional licence.
If you now want a CPL, then it would be possible by completing what amounts to the shortfall in SE & ME flying, and the appropriate flight tests for CPL issue. If a single pilot IR is required, then the initial iRST is necessary. Plug the gaps to achieve the minimum experience.
You are best to discuss this with an ATO who have MPL experience.
Last edited by parkfell; 17th April 2016 at 06:44.
Reason: Syntax