rosie plum, Borassum and Emma
Many thanks for your responses.
Borassus - I thank you for your politeness in describing this plant as not looking particularly robust!. I do agree that the plant was not in ideal conditions. The soil appeared fairly good at time of planting (pH 6-7) but the positioning was semi-shade for part of the day and north-facing. However, although the plant bed was situated north-facing, this is a town garden surrounded by tall buildings and the sun from 11.30am-8pm mid-summer can be extremely warm) and the plant was open to the sunshine during these hours. It has not grown at all in the past 3 years but it's neighbours (astilbe, pieris, aucuba, bay laurel) all planted at the same time, have thrived. I only began tackling the garden 3 years ago so I am sure that my beginner experience is responsible for this failure in not knowing how to respond, certainly not in a timely fashion, to seeing a plant in distress.
I also agree with Emma about the vine weevil in that the disappearance of the roots has been severe. It is no exaggeration to say that all that is left is one 1cm thick main root about 6cm long and a series of extremely delicate looking hair-like attachments - which makes it astonishing to me that there are signs of new leaf growth now. The original roots have most definitely gone. There is so little there that it would have been easy to spot any 'can be seen with the naked eye' type pests and it's probable that there has been considerable eating going on over a long period of time. I ought to have cottoned on to the possibility much earlier.
It is now in a warm sunny spot and I will nurse it over the summer months and hope to see some revitalisation. I'm assuming that it does take even a healthy Choisya a few years to give bushy growth and height? It would be informative to know how much growth a good healthy plant would be expected to produce in a year.
Thank you again for your appreciated responses. It's very helpful, encouraging and a good learning experience.