I am on really heavy clay, spends part of its time waterlogged and when it dries, it's rock hard! But I grow Bottle Brush, Flowering currant-yellow and pink, lilac, and loads more, buddleia grows anywhere and they say roses love clay. If you need a hedge you could try Rosa Rugosa, but it creeps and is lethal with the thorns!
I shall watch this with interest to see what is suggested.

Thanks Honeysuckle, can you tell me is Rosa Rugosa evergreen? Because I am looking for it to form an hedge.

I had exactly the same problem with Escallonia Iveyi, kept feeding with Epsom Salts, Magnesium, but replaced it with taxus (yew), which grew quite quickly and looks really good when clipped. Portuguese laurel, Prunus Lusitanica‎ would be quicker growing and would also fit the bill. Wouldn't hurt to dig in some grit when replanting.

Otherwise, if you want some flowers, Berberis darwinii or the ubiquitous and thorny Pyracantha - the latter is often sold at easily a foot high in its pot already. Neither's particularly fast growing though, average growth rate. Photinia fraserii Red Robin is another possibility, but again, average growth rate.

Thanks, folks some food for thought there.

Unfortunately, Escallonia is being decimated country-wide by Escallonia leaf spot - https://www.rhs.org.uk/advice/profile?pid=108 - and there's currently no treatment for it. I binned my Iveyi and Red Elf last year, and replaced them with Photinia fraserii Red Robin, which is a very fast grower (here in SE Wales, at least) and is fine on clay.

Rugosa roses aren't evergreen, by the way.

Beware of fast growing ones though because being vigorous they don't respect your ideas about height and you'll be forever clipping them.

Lonicera nitida has very small densely spaced leaves and makes a very neat evergreen hedge and there are both dark green and golden varieties. Its very plain but makes a nice background for flowers in front of it.

I'm not worried about how high it gets Steragram, I'm retired now and I have all the time in the world. I will certainly look this one up, thanks a million.