They're pretty hardy but if its very young remember to throw some fleece over it if the temp. gets below freezing in your greenhouse.
Remember small pots get cold quicker than big ones. I'd just pot it up into one size bigger pot if you can see roots coming out the bottom and keep in greenhouse over winter then harden it off in spring like any other plant and let it spend summer in the warmest place you've got. Put back in the greenhouse next winter if it looks a bit too nippy but 0--4/5 isn't much of a problem. Late May frost nipped mine's leaves last year :( but it still fruited ok.