If it is dormant, you can do it now. I would give it a final resting place in an 18-20 inch pot at least 12 inches deep. I you wish to you can place the pot on top of a stand with wheels so you can easily move it if you need to. Some grape varieties do better potted than others so if you know which variety you have, check it out. A few years later, you can take cuttings from your vine for further propagation when the vine is dormant too.

Hi, grape vines are fully hardy, so can be grown outdoors, unfortunately our summers are not usually long enough to ripen the fruit, so most often the plant is in ground outside the greenhouse, with just the vine itself inside, to help with ripening the fruit, this may be an option you could take, rather than growing in a pot, which is not an ideal situation, Derek.

I agree with Derekm. I can't imagine growing a grapevine in a pot and expecting it to do well and in a greenhouse. They consume an incredible amount of food and water and grow quite rapidly and hate being transplanted or moved around. They need access to those trace elements in the ground for proper fruit set. Consider the vineyards of the Rhône Valley; Southern France.

I used to have one in a lean-to conservatory. The big woody stem was outside but the main stem came in thru a pipe sized hole in the wall & then was trained on wires over the ceiling area - it was a success.