Gaddy,
If I was you I would go and see a decorative concrete supplies place. (South Coast Decorative Concrete Supplies are down your way) There are sealers that can be applied in around 28 days. You could also get it in colour. A light colour would be good to bounce light around, especially if you get rid of the skylights. They will also give you the run down on the non slip additives available. I think, stay away from the ground glass option as I think this will wear off with trolley jacks etc because it sits on top. There is one that you mix into the drum and its like a silicone powder. It looks like it would do nothing but it does.
I really wish I had of done this with my shed before I spilled oil and crap everywhere.

PS Shed is looking great!
Chris