apple tree

The maggots are the larvae of the coddling moth. Spray and prune in the winter time. Meanwhile harvest what you can of your crop, you can cook them and make puree.

You can buy a pheromone trap for these which you hang in the tree in the spring, from what I recall - it works, no pesticides in the air or on the tree. Ask your garden centre if they still have them.

Thank you Bamboo. Advice is really welcome.

the maggots are infant coddling moth, the brown stuff is 'frass'.

pest lifecycle;

eggs are laid in the freshly opened blossom buds in spring, the maggots hatch and grow in the developing fruit, eating their way out and hibernating in the soil underneath until emerging the next year as adults i think. check to see if there is a hole in the basal floret of the fruit ( Where the blossom petals used to be before the fruit developed) aswell as the side of the fruit.
fork over the soil at the base of the tree and encourage the birds to peck there in winter and spring.
also get hold of the pheremone traps
try to break the lifecycle of the pest and do so organically if possible.

regards from james