I have planted him in ericaceous compost hoping this will do the trick

Whatever it is, it needs to come out of that pot and go in the garden, that's probably the reason it's getting smaller. I don't think it will get any better or reach its full potential until you do.

Ok thanks. I may do that as I got nothing to lose the way its going

Something seems to be nibling its leaves?

It also looks pretty dry. Is it a camelia? I have a container camelia, lives in it's pot, but I do keep it really well watered. Flowers beautifully every year.

. . . . oh, I've just zoomed the photo. It might be an escallonia. and if so, I've not managed to keep them in containers.

Hi, welcome to GoY, I can't tell what it is from the leaves, but whatever it is, it looks as though it's going to be more trouble than it's worth, it looks as though it may be some kind of shrub, in which case it's going to be quite a while before it looks anything like a decent plant, I think if it were mine, I would cut my losses, and dump it, sorry, Derek.