Never realised you could redeem the Witcher 1 keys until now, However when I go to redeem my key from Steam i'm getting a key invalid message, The game itself works fine through the steam client, any ideas?

Try here: http://www.thewitcher.com/backup/

Go to this site, and follow the instructions therein. Basically, assuming you still have your email from Steam from when you bought the game, you'll need to print it out, write on the paper your email address, the unique code from that page, and your signature, and then scan it / take a picture of it and send it in via the page's form. They should get back to you within a day or two.

This is what I did, and now I have my own copy on my GOG shelf. If you don't have the confirmation email for whatever reason, I believe that you have to make your Steam profile public, send in the request, and wait for them to actually look at your profile to see if the game shows up.

Thanks, submitted a request.

Incase anyone got the witcher1 as a gift on steam like i did, I toke a screenshot of the gift email beside the my steam library clicked on the witcher with the cd key showing and sent that to them.