987056,
You really do need to get hold of a copy of the aforementioned Caves of Gower. If you ask Tony really nicely I'm sure he might even consider reducing the price for you!
You mention Swansea Library - I recall that the old Reference Library used to have a fair bit of caving related stuff including early SWCC newsletters (although these are all on-line now anyway).
Your other prime source for material should be the SWCC Library itself - I'm sure if you contact someone on the Committee and tell them you have a serious research project in mind then you would be able to obtain access (probably on a weekend when a key would be more readily available).
Where are you based? PM me if you fancy coming digging down on the Gower sometime.