Looks like a Garden Carpet Xanthoroe fluctuata according to my Complete British Insects ( Chinery 2005 in Collins Books ). It attracted me by its smart contrasting markings. Would have found it quicker if I'd known to look in the 'carpet' group! It was quite a small moth, and when I released it on the outside of the window, there was another, this one a bit less 'contrasty.'
Its food plants are crucifers, cultivated and wild. I've got plenty of those - cabbages and brocolli full of holes - rocket helpfully self-seeding all over, and weeds like Thale Cress. I don't fuss about weeds too much these days. Crucifer comes from 'cross'. All the plants in this huge family have four-petalled flowers, making a cross shape.
Above - Garden Carpet ? - Halifax
You don't often get an apple with a 'worm' in it these days, probably because the growers spray everything that flies and crawls. These tunnels in my crab-apples might have been made by Codlin Moth larvae? (Cydia pomonella.) They were the first to fall off the tree. I'll have a look on the tree tomorrow and see if I can spot any mis-shapen ones that might still have a larva inside.
I'm prepared to be corrected on my identifications. . . . . .