This sounds to me like 'soil sickness', which usually occurs with roses, when a new rose bush is planted in the space where one used to be. Whether it occurs with other species, I'm not certain, but you could try the remedy with your hebe.
Dig out the old soil from the planting site as deep as you can go, 60-70cm should be ok, unless you hit subsoil. If you do, don't mix subsoil with topsoil. Break up the bottom of the hole with a fork and mix in some good quality compost. Dispose of the old soil in another part of the garden; don't re-use it for this planting.
Add a small handful of fish/blood/bone or Osmocote to the new compost and stir well in. (Sounds like a cake recipe!) Water the mix in the hole and let it stand for an hour. Then plant your Hebe, ensuring any old compost is washed off the roots. Tread the shrub in lightly, and water well, to ensure the compost is settled round the roots. All the best. Bbb.

Wow.....Bbb that sounds like good advice I will pass that on. As I said she did dig the ground again before planting, but not to the point of actually removing the soil,will give it ago. Cheers

Is it Hebe heartbreaker? I had one that never got going properly & I threw it out after some years. Well named as far as I was concerned! Hope the soil replacement works for you.