Sebastian's family say his treatment was a "miracle"
Surgeons at the Royal Children's Hospital, in Melbourne, removed a nerve tissue lump the size of a large grape from nine-year-old's brain during a five-hour operation.
The family are hailing Sebastian's treatment as a "miracle".
He is due to fly into Heathrow Airport early on Thursday mornig.
Life transformation
His mother Anna, thanked the surgical team led by Professor Jeffrey Rosenfeld, for giving them back a "new boy".
Before the operation, in June, Sebastian used to have painful epileptic seizures almost every day.
It also affected his appetite, emotions and behaviour and his ability to speak and walk.
Now Mrs Selo said Sebastian can go for long periods without any seizures.
"It is an Australian miracle because when we were coming here we only expected that perhaps a big part of the tumour would be removed and we didn't have any other expectations.
"This has gone beyond our imagination and our dreams because all our prayers have been answered. The whole tumour has been removed totally and successfully.
"Sebastian goes for very long periods of time with no seizures, like never before in his life."
Vast improvement
The family said that since the operation Sebastian has become more loving and responsive and that his movement, speech and sight had improved.
His father Louie Selo, said the whole visit to Australia had been beyond expectation.
"We could not have predicted the amount of publicity, goodwill and the amount of interest in Sebastian's story. If I had dreamed this I would not have believed it."
The Australian medical team has built up an international reputation for their brain tumour surgery and since May last year have carried out operations like this on one child a month.
During Sebastian's operation, doctors made incisions from the top of the brain instead of the base to avoid nerves and arteries, and to lessen the danger of a stroke occurring.