can I move a gunnera that has out grown its pot and put in the ground now?

Gunneras are best planted late spring when the risk of frost has past do that they have a summer in which to get established. Even so they will still need protection over winter. When the leaves die back they should be cut off which will reveal the buds which should be packed with straw and the old leaves wrapped around them. Rather than put your plant in the ground now it's best to leave it in the pot, prepare it as above, and put the plant in a frost free place until you plant it out next May.

I would not put it in the ground now, not with winter coming on as it will not survive the shock. It will over winter just fine with an occasional feed and being kept moist.If you want to try it in the ground next spring will be better when the risk of frosts has gone.

You could get away with re potting it into a bigger pot with a good quality compost though.

No if its in the ground you cant move it without ripping its roots and killing it.