Shrubs outgrowing space
As a novice (clueless!) gardener I planted a Choisya ternata and an hypercium. I allowed them each around 1m to 1.5m to grow in but they are stil growing into each other. It's possible that I didn't leave enough space for the Choisya which I think could get to 2.5m spread I think. At some point, will they suffer from being so close together? Apart from a lot of pruning, am I likely to have any other issues?
Luckily, both can be pruned as and when they need it without real detriment. You might lose a few flowers but both will quickly grow new shoots.
I quite like shrubs growing into each other, it suggests lushness. How long do you plan to be in this house?
They are both thuggish plants and can tolerate serious hacking back and they will still grow with vengeance. It depends on how big your garden is as to how much space you allow them to grow. I would not want them in a small garden is all I can say.
Personally I wouldnt call them thuggish - They're just plants with the potential to reach a decent size without too much TLC - 'good do-ers ' is what I'd call them. Easy enough to control with the secateurs.
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
I agree with dove, they are easy plants to keep reasonably small.
I would see if you do have problems first and if you do, then decide which you like better (for me it would be the choisya) and remove the other one.
This would leave you a space that you can choose a replacement to fit. Have you seen these: http://www.crocus.co.uk/plants/_/berberis-thunbergii-f-atropurpurea-helmond-pillar/classid.315/
If your Choisya is Sundance then this would look stunning but then that's my personal preferences coming through.
Hope this helps put another perspective forward.