What is it and what is wrong with it - any ideas please?

If you have google on your phone you can go into google search, press the camera picture in the right hand side of the search box and take a picture. Google will then search and tell you what the plant is called! Not sure it will explain the spots though

Errata - sunscald not scale !

Much loved by florists, Pittosporums come from your part of the world and are pretty tough .
I have massive hedges of them .
I wouldn't grow it in a pot - can it be planted out ? If you must then repot with fresh compost and a slightly bigger pot .
They don't like dry nor soggy soil .
Jumblygran from NZ has excellent advice and I'd follow her use of Super Shield .

Mine occasionally have spots ,which I attribute to sunscale .
They get regular pruning as I use them for bouquets .

You could cut the offending shoots with sterilised secateurs.

35 years on and grown from seed they are still growing well .

Two things. Firstly, Pittisporums don't like wet roots and damp. Secondly they can be prone to leaf spots especially if planted in areas with high rainfall and/or humid conditions and minimal air circulation. I would not use chemicals. Make sure the plant has good drainage. If you must have it in a pot add grit to the compost to help drainage and don't overwater. Also, thin it out a little, prune out the worse affected branches to get some air around the leaves. Then, if the roots are happy it should thrive. The north facing location isn't a problem. I have a vigourous Pittisporum in the ground on a north wall. It gets plenty of light but no sun.

It's a Pittosporum and they are prone to spotted leaves.

The single best way to keep all plants healthy is to improve the soil/compost they are in and to water them well, but not let them become sodden - they really don't like sitting in waterlogged soil. Also make sure your plant gets enough sun - they like sun or partial shade but not full shade.

I reckon if you do this in a few months you will see a much healthier looking plant without having to resort to using chemical treatments.

Rose Clear is toxic stuff. Not good for pets or children and a nightmare for insects. Sorry to rant but I am a passionate organic gardener and believe these things are messing up the systems in our gardens and environment.

I would replant in a bigger container I replant my plants most years.

Oh thank you all so much. I haven't owned the shrub long enough to know if it produces flowers of any kind but I do have some Rose Clear left by the previous house owners so perhaps that will do the trick. Do you think I should replant in fresh compost in case the old stuff is harbouring the disease?

It is a pittosporum I have a hedge of them and have had the same problem. I am in NZ where they are native, but. I guess the treatment would be the same. I spray it with the same spray
I use for the roses. Over here it is called Super Shield and it is both a fungicide and an insecticide.
This has worked well.

Looks like a pittosporum to me too. I think it's likely a fungal disease ?

It might be a Pittisporum (not sure of spelling). Does it produce tiny black flowers?

It's only a suggestion a variegated Hebes plant with black spot a fungal infection ?