Probably not very successfully, sounds like the Choisya has been in situ for longer than 3 or 4 years. If you wanted to try, the best time is autumn, not now - if you tried it now, you'd need to cut down the top growth by two thirds to give it the best chance of surviving the move, and keep it well watered right up till autumn.

Thank you, Bamboo. I really don't know what to do with this gap. Even if the choisya grows in on its right hand side, which would make it look better, it really is too close to the red robin on its left (just out of the photo) and I'm continually having to hack them both back away from each other.

Not sure whether I should cut my losses, take it out altogether, and plant something in the middle of the gap, leaving plenty of room for growth.

It seems such a shame, though.

I hesitated to suggest that, but that's what I'd do, this time checking the spread measurement of whatever shrub you choose. You can certainly reshape whichever one is left by cutting it back hard - it should then grow in a better shape. Maybe choose Choisya 'Aztec Pearl' - the dark green thinner leaves will contrast well with both the photinia and the Choisya sundance already there. Or even a hydrangea if there's enough moisture for it in that bed, and you don't mind a deciduous shrub there - Hydrangea paniculata 'Wim's Red' gets about the same size as the Choisya, and can be pruned hard every year(unlike the mophead types).

I have moved large choisyas on quite a few occasions over the years all were successfull, on one occasion I moved one on a blistering hot day, the client insisted I do this having told her it possibly would not take, but a ho it survived, how I did this was to prepare a very large hole and filled it with well rotted compost and watered thoroughly, then the lower stems I removed so I could get a decent rootball, once I had dug it out I put it in its new position and firmed in, yes it sulked but only slightly and I insisted that the client kept it well watered and this was done on a very hot day where the weather stayed very hot for a week or so, it still looks great, it gets a good renovation prune every so often, so don’t be afraid, just get a good rootball, don’t let it get misshapen, give them a good prune, do it now or after it flowers it will respond very well to renovation pruning.

Thank you both for your suggestions, Julien I have only just seen your response, apologies.

I kept the choiysia in the end, and planted a spotted laurel in the gap. The choisya is starting to fill in a bit on the side, but I'm now about to ask another question - will start a new thread, though!