Historical railway usage Data

I want to collect data on the historic usage of the rail network through the 20th century, specifically closed branches in the West country. Ideally I'd need at least one set of data per decade and of course the more plots the better. I've seen something similar in some the more recent Middleton PRess publications, which include tables of comparative station stats on passengers and freight (in and out) for individual stations. I'm guessing this information might be available in the Annual Returns compiled by the Railway Clearing House - but before I spend days in Kew wading through thousands of documents I wondered if anyone has been there before me and perhaps can help with a more specific reference and confirm which actual publications contain these data?
Thanks in Advance! - Andy.