You can do it now as long as you're prepared to water it thoroughly for the next 4 months or so every time its dry. Good luck with it - it will have a pretty big rootball and may be very difficult to get out intact. You may also need to reduce the topgrowth by a third.

Thank you very much for your reply. Can I just clarify, I may need to cut it back a third? Why is this required? As you can gather my knowledge of gardening is very limited.

Well, when you try (very hard, I expect) to dig it out, you will find that the roots are extensive and spread a fair distance - I'm assuming this because Pieris is slow growing, so if yours has reached five feet, it must have been in situ for some years. I personally wouldn't attempt such a move with such a mature plant, but if you want to have a go, do - you will need to start digging about 2 to 3 feet out from the centre of plant, easing the soil and loosening it as you go, working all round. You may need to spade some soil out of the way to get the central part of the rootball out, but you will, no matter how careful you are, inevitably break some roots, probably quite a lot. So the reason you reduce the topgrowth is so that the plant's roots don't have so much growth to support, as this is an evergreen plant. You may even need to reduce it by half if it starts to droop.

Now I understand. Well here goes, many thanks again.

The Piertis is shallow rooted and, for a five foot plant, the roots will be massive.