Apple scab. Very prevalent this year because of the weather. Spray with Copper sulphate if you can still get it or otherwise you may be into using something like Rose Clear. Needs to be done from once the flowers have finished at 2 week interludes until a few weeks before picking. You might be lucky and not get it at all next year.
Moving a tree is always a problem, but it will not have made a lot of spreading roots yet. As big a soil ball as possible when the tree is dormant is your best option. You may lose fruit next season though.

Thank you for your very helpful reply.