I've messed about with creating a new theme, I've picked my templete to
start from (slate in this case), I copied the folder, edited the appropriate
files, edited sptheme and sure enough the new themes listed in the list in
sharepoint.

I editing the site via frontpage and applied the theme to my site, I then
customised the theme and reapplied it. Saved the theme as the same name as
my custom theme.

This has saved the latest revision of the theme on my local workstation and
left the copy of slate on the server unchanged.

How can I transfer the latest theme from my local frontpage to the server so
that for new sites I don't have to edit in frontpage, apply the theme and
then save back to the server?