As far as i know GEM updates are only avaliable if VSE is managed via EPO.
Oh. What I'm after is setting the AutoUpdate Repository to the CD drive, then putting a CD with the latest gem files in and hitting Update Now.
I've heard it works...
Wouldn't have thought so.
There are a load of other files VSE uses to validate the authentisity of the GEMs. There are a few ini files containing MD5 hashes and checksums that are auto-generated by EPO so that VSE knows the GEM files haven't been tampered with.
It might be possible (and what you might have heard) to copy all the gems and these ini files from an EPO server and burn them to CD and update that way but either way you would still need an EPO installation