Move it in late autumn/early winter with a good rootball and it should be fine.

Don't expect it to come true from the pip! We were very disappointed having collected the pips from a John Downie crab, which we grew on over six years. This year the tree has produced flowers only they are like an ordinary green crab, not the pretty yellow fruit you'd expect. 'Proper' apples would be even less likely to succeed though you might be the one in the million to produce the new 'seedling' which has something special about it.