You Be Mother by Meg Mason

The only thing Abi ever wanted was a proper family. So when she falls pregnant by an Australian exchange student in London, she cannot pack up her old life in Croydon fast enough, to start all over in Sydney and make her own family.

It is not until she arrives, with three-week-old Jude in tow, that Abi realises Stu is not quite ready to be a father after all. And he is the only person she knows in this hot, dazzling, confusing city, where the job of making friends is turning out to be harder than she thought.

That is, until she meets Phyllida, her wealthy, charming, imperious older neighbour, and they become almost like mother and daughter.

If only Abi had not told Phil that teeny tiny small lie, the very first day they met…