You’ve just reminded me that I must prune the young kiwi we have in the greenhouse at Stephanie’s Kitchen Garden.
You are correct in that kiwis need annual pruning and lots of space. They should be trained as an espalier along a wall or a fence - I’ve included a link from the RHS website detailing exactly how to prune. http://apps.rhs.org.uk/advicesearch/profile.aspx?pid=600
You did the right thing in bringing your kiwi plant into the greenhouse, they are tender to winter frosts so it should like the warmer conditions of the greenhouse. Harrod stocks many different kinds of heaters to suit all needs.
The ‘Jenny’ variety that you have is self fertile so you don’t have to worry about pollination from another plant. Given the right conditions you should start to get fruit after 3-4 years so don’t give up on it yet.