Hi
From what you describe, considering the data volume only, it does not seem to me that you would require to use access instead of excel. Also, since the only functionality mentioned is the use of pivot tables to analyse data, again excel seems to be a good response.
I will be happy to help you create an excel allowing you to store your accounts users and products, as well as to create templates in the same file as well as pivot tables.
I am also including in this bid a remote skype base demo of how to create pivot table yourself so that you are independent in the future to evolve the excel file.
Finally I am familiar with some free software tools for analysing data, with some more information about you analysis needs / requirements I would be able to give some suggestions to which ones that would best respond to your needs / requirements.