Thank you Marvelman.

I just found an article online, from 2017, about effectively splitting the BTC account (into BTC and BCH and that way claiming BCH) directly in Ledger, rather than having to use Electron Cash or anything external. However, the article is old, and references a Ledger Manager and BTC Wallet apps, which no longer exist and have been replaced by Ledger Live. Does anyone know if this is still possible? I searched the help articles on Ledger's website, but haven't found anything definitive. If possible, this sounds like the most straightforward way to go about claiming BCH.

And regarding BSV, which I'm just reading about... I understand there was a BCH hard fork about two weeks ago. Can I claim BSV too, or do I have to have claimed BCH FIRST, before 15th November? Or is it enough to have owned BTC prior to 15th November, regardless of whether I claimed BCH or not?

This is all a steep learning curve! 

Sorry for all the questions, and many thanks to everyone who has already contributed!