As this seems to be getting more involved I will explain what I have done.
I purchased the key.
I was then directed to cnet to download a 300k file, I ran it, there was a small update to the program, My code arrived in the email, I copied and pasted it into the program. I was told the key had been loaded ok.
It looked like I have already explained, So I went to the avast site and downloaded the full pro version and installed it, And it still says home edition on the about page, but, I do have the script scanner running that suggests I have pro running, its just the program itself does not say pro but home.
And yes, there have been several restarts since.
Cheers.