Planting any tree once it’s in full leaf is going to be difficult rosiegirl.
The act of planting will shock and damage the roots to some extent and there will be a pause then where the leaves lose water through transpiration faster than the roots can replace it. Result..leaf desiccation.
However...you have also got Cherry leaf spot disease which is caused by a fungus.
You’ll have to spray your tree with a protective anti-fungus spray to keep any young leaves safe from infection as they open.
Check at your local garden centre for a fungicide that can deal with this disease, afraid I can’t suggest what to use as this side of the pond has different regulations to you.
Keep a steady watering programme going and hopefully the tree will recover and get going.