Thanks for both replies.
Holding down the select button on an ePUB title on my device doesn't give me any reader options. Presumably only the FBReader comes as standard.
I've been to http://www.greenreader.co.uk/pages/support
and downloaded the update.
There's NO instructions on what to do with the ZIP file, so I figured that I should copy the contents to the root of the device... nothing new happened, even when I switched off and on again.
Earlier, when I went to the global site, I just got a .BIN in the ZIP, which I copied to the BIN folder... nothing happened.
Looks like some instructions on the site are needed.