eucalypus tree

[sadle]

when is the best time to move these trees

[Thunderbird+]

Now is a good time to move it, as long as there is no danger of frost.
If its a fairly large tree, it may not make a good root system and can be prone to blowing over, in this case buying a smaller pot grown tree may be a safer option.
If you are moving it further away from your house, this is a wise decision, as a rule of thumb trees should Not be planted any less than 3/4 of their mature height, is will vary according to the species of eucalyptus, E. gunnii can reach 40m in the UK (you do the math's)
You can however keep them small and compact if you coppice them, this is cutting them down close to the ground on a regular basis, this way they will only produce the attractive juvenile folliage and will not get out of hand as long as you are prepaired to keep it maintained.
Good Luck Tbird+