HELP data can be directly accessed on the Herschel Database in Marseille:

The raw files can be extremely large. For some of the final data products it is also possible to query the data from the Virtual Observatory database:

The structure of the database server and the code used to perform the reduction is all stored on GitHub which contains extensive documentation including in the Jupyter notebooks used to execute the code. The GitHub pages are probably the best place to find details about the data used and how the final database is structured. We also encourage reuse of all the code there. Please contact us with any queries by creating a GitHub issue.