Hi Waka
I do floors often and use the Rustin's water based floor varnish almost always (have done now for about 6-7 years). Five coats, 3-4 hours in between coats and a light sanding.
Despite Noel's reservations about water-based finishes, I have found the finish to be very tough! I had to sand some of the varnish off last week to make a repair to a floor I originally sanded 3 years ago and I was really surprised at how difficult it was to grind away the finish. Floors that I did years ago in gloss still look as good as new. The satin finish is less resiliant. (One trick is not to stir the last coat of a satin finish - it makes it slightly more glossy, but tougher).
Other suitable products are Floor lacquer (from Richard Barry) which is the real deal, used for dance studios and the like, and Rustins 2-part finish. Dulux do a "Diamond hard" finish (still water based) which I've used once or twice. It's good, but no better than Rustins and more expensive.