we are about to revarnish our nms 4 deck and not sure what varnish is the best : we do not have a great deal of time to mess about with the different type of hardners so is there any quick but effective way of doing this

The type of boat is immaterial. In this respect if not in others all boats with wooden decks are the same. So it's just a matter of talking to your chandler who may or may not be able to advise, or going on line and looking at various manufacturers technical data!

If time is of the essence i would use International Goldspar, 3 coats possible in a day coating when the prefious coat is still tacky, use a roller and Jenny brush

I'm not sure i'd put 3 coats wet on tacky.

Personally i'd use two pack, the new perfection plus from international is an excellent product and an easy 2:1 mix.

There is no quick way at this time of year unless you heat the workshop.