Cherimoya or custard apple although is a native to Peru and although considered  a sub-tropical  tree it can take down to -3 degrees once established. Protect when younger from wind and frosts and plant in a warm sunny spot . If space is an issue they are stunning espaliered or even grown in a container.  Generally speaking , rule of thumb , you can grow a Cherimoya anywhere you grow lemons. The fruit ripens in September to November and  are considered on of the most exquisite fruits in the world! Simply put they just melt in your mouth, the creamy , white , soft , sweet and juicy flesh is a cross between a passionfruit, papaya , banana and pineapple. Absolutely delicious!