Would it be ok to prune this gum tree back to make a bush

Yes you can trim/prune it and the young leaves look the best. They can grow very quickly to a great height if not. Liable to falling over in high winds when very tall. They copice very well.

Is it the right time of year ?

I would do it in early spring. The foliage really changes as it gets bigger and older, the nicest leaf is on trimmed bushes. We had three and ours got so big (height above the house) we had to have them removed I wanted them as small treees but they got away from me.

As Drc says, do it in Spring - where you live, probably late March. Take it down to the ground if you want and let it regrow, but watch out for apical domination - there will always be a lead shoot heading for the sky! Should put on 6/8 feet of growth in a season.

Thats what scares me,I'll leave it till the spring then i'll have a go,Thanxs :o))xx

I used to chop the top off one of mine, and kept another as a shrub, cutting it back to the ground every Spring, which kept it within bounds. By cutting the top off you can decide just where the crown begins and you can keep it to a height you can manage every year.

Oh Mad I wish I had done that as I think the young leaves are so attractive perhaps I should try again to grow one as a bush.

I think the leaves omit a smell that keeps knats /midgies ? away on hot Summer nights ,but as we have'nt had any nights like that i dont know:o((

Can't say I noticed that when I had one in my garden, Swanky - in fact, you can't smell it at all unless you bruise the leaves. Be nice if it was true though.