Hi Tom and Mary. I wouldn't bother with the fruit thinning, that'll occur naturally. The main concern is the wilting branches. 3 main things spring to my mind.
1 there is damage to the bark by wind chaffing,
2 canker- a kind of sore which when spreads around the circumference of the branch will prevent fluids from reaching the branch and it dies like the wind chaffing.
3 by far the most serious and I don't know if it is too late for it to happen, but it could be erwinia (fire blight). It is a bacterial infection carried by the bees during pollination and enters thru the flowers and causes quick die back.
I would remove the die back and burn it and make sure you sterilize cutting impliments during and after use. I am not sure about U.K regulations but Fire Blight used 'have to' be reported to Ministery/Dept of Agriculture, because of the threat to the economy and environment. Don't worry though, they won't come in spaceman suits to your garden, it is just to track the spread and quantity of outbreaks. I hope I haven't been too scary. It does point out though how easily our economy and environment ie apples, pears, hawthorn and other members of the rose family could be wiped out by a simple action as pollination. Take care and I hope ye will Discovery a solution. Din
Thanks - I had considered fire blight (with fingers very much crossed). It looks a little similar but doesn't have the burned appearance. Some of the leaves have developed brown spots, but this could be because they are dying.
I think I'll go for the removal and destroy option.