which iris is it? is it the type with the large surface rhizome germanica? if yes then you should have several 'branches' of rhizome. each piece can be cut off and replanted at the same depth as it was as a whole plant. cut the foliage down to about 6-9" to help reduce wind rock and water loss. I tend to do mine August when I have space to pot up the new bits ready to grow on to sell next year.

if its a bulbulous one like latifolia then you have bulbs that you can lift after the leaves have yellowed split like you would daffs etc replant and ''job's a good'un''

ty seaburngirl,its the first one and its about 3ft by 4ft around,you make it sound so easy i will give it a go in aug,ty chris

oh trust me it is really easy. just worked out ty is thank you doh!