Before deciding to interrupt, it is incredibly important to read all of the information available to you here- Interruption Information
If your grades have not been confirmed at a Progression and Award Board Meeting (PAB) before your interruption request is processed, when you return to your studies after your period of interruption, you will essentially be starting your academic year again. You will need to submit all your assignments and receive new grades and an updated results letter.
If you have been presented at the PAB before your interruption is processed, then you are able to carry your grades over.