If the one you have is definitely Pieris japonica 'variegata', this one needs a fair bit of sun. It's also slower growing and not quite as hardy as the plain green forms, though it is hardy. Leave it as it is for now, but do any pruning you need to do in spring - you can wait for the flowers to fade if you like, otherwise, just prune once all risk of frost is past.

Thank you, Bamboo. I am afraid I had kept it quite shaded, as I used to have loads of lovely, big, healthy Pieris back in the UK which were planted in almost total shade, but of course they weren't variegated. Silly me. Will it survive a quite radical prune, do you think?

There is quite a lot of confusion about Pieris - they're known as shade lovers, but actually, that only applies to Pieris formosa varieties, such as Forest Flame. The Pieris japonica varieties like a bit of sun.
I should think a good prune would be okay - I once forgot to water a potted one and it did what yours has done. I was going to bin it, but the lady next door took it, cut it back where necessary and fed and watered and I understand passed it to her daughter for her garden, where, as far as I know, its still thriving.

Thank you, Bamboo - There's still hope for me and my unfortunate plants, then?

Where there's life, there's hope, Gattina.