Hi Gareth,
Have you had a look at the DVTk Modality Emulator (https://www.dvtk.org/)? You’ll have to register to download the installer or you can download the source code from Github (GitHub - dvtk-org/DVTk: DICOM Validation Toolkit).
You could also look at ‘jdicom’ which also has a modality emulator (JDICOM).
Paul