I posted a request earlier to no avail and I've ploughed through a ton of stuff to get the install working :)

Its suprisingly easy (once you know how!).

Using a cPanel upload your C5 zip (to a private area) e.g. not your public_docs or public_html).

Again using cPanel, unzip the file (again do this in your private area)

You'll get a folder (in this case named 5331 or similar). Now take all the files in this folder and move them to your public_html (or equiv)

Back to cPanel to edit your htmldiff.py file and "chmod permsissions to 755" <- this sounds scary but using cPanel I fiddled about till I figured what 755 actually required!

Then back to cPanel, create your mySQL database, remembering to add a user (which I didnt for few frustrating hours!) I used the cPanel wizard to generate the password.

Now you can goto to your temporary URL (assuming your completely new like me) and you should get your C5 install screen.
(I didnt at first as I hadnt copied all my files to the root of public_html)

Enter the database name, user and so on, tada, success.

I hope this helps others get going. Once working this is easily the best CMS solution I've tested. Now to do some shopping for add-ons....blog, testimonials, tabbed content....