Build and Update Utility (BUU) can't load repository, "Invalid Repository" (PE1850) on firmware update

[Joel Duckworth]

I'm trying to get the BUU working for firmware updates from a
repository. I've created a custom repository from Content Manager using
the online source, of a PE1850 with both linux and windows updates. I've
tried putting this onto a DVD & USB key but both times the BUU is
telling me "Invalid Repository..." and something about not having the
correct repository for the hardware, when I try to run a firmware
update. I've tried recreating the repository a few times but still it
doesn't work. It doesn't mention in the documentation which folder you
should put onto the DVD or USB key. I've tried the CustomRepository
folder as the root and then also what's inside that as the root, and
finally just the 'repository' folder as the root. Still no joy

Also I've tried running updates on the repositories that have been
downloaded. It detects whats in the repository (PE1850 windows, linux)
but all the versions are just '-' with the old and the new and you can't
do anything more. Any help would be much appreciated!

Regards, Joel Duckworth