We've all had a variety of experiences and I respect what both heathfield and AIBags have to say... but, before you make a decision you should at least read up on Spar Varnish... often called Marine Varnish (at least here in the U.S.
It's made to withstand use on boat decks and spars (hence the name). Additionally, if you scratch or otherwise damage many of the poly finishes, they are really difficult to "spot" repair... at least in my experience, whereas spar varnish can be fixed locally fairly easily.
One caveat.. make sure the floor is absolutely dust or small debris free. Secondly, if you do use spar varnish, don't overwork it when brushing it on... it'll cause small bubbles. It flows out very well so use a really good chisel edge brush and dont work it very much... Best of luck!