@piers.batchelor Its seems your use case may not be a chat bot Would that be right?
By reading your description it sound like you want to take a document and do some sort of analysis on its content. Is this correct, or are you are trying to ask questions about parts of the document (They require different solutions)
a) Chatbot trained on large body of text
b) Analyse content of a large body of text
c) ask questions about a large body of text (similar to a - but no back and forth discussion)