By Caroline Parkinson
Health reporter, BBC News
Eight-year-old Tomas Erickson-Antazana is like any boy of his age.
He loves computers, mobile phones - and Basil Brush saying boom, boom!
Tomas halfway through his treatment,
But it is only recently that he has had the confidence to be among children of his own age.
Tomas from Bolivia was born with a severe facial disfigurement.
He had a hairy neavus, patch of skin which almost covered his left cheek which is like a large mole but which is also covered in thick dark hair.
It meant that Tomas, who grew up on the street, had a significantly increased risk of skin cancer.
He had also been severely abused by his mother, and was living in the Bolivian Children's Mission orphanage in Cochabamba when he was brought to the attention of the Facing the World charity.
Tomas came to the UK in August and has had two operations; one to remove the neavus and another where an implant was placed behind his ear to encourage extra skin to grow to cover the area.
He is due to have his third and final operation, which will hide his scar as much as possible this week.
Delia Moorhouse, who runs the orphanage and who came to the UK with Tomas, said: "Before, he was shy in a lot of ways. In Bolivia, we'd had to take him out of school for a week because he was picked on by the other children."
"He's a lot more out-going now he's had the operation.
"And he loves the attention he gets when he goes to hospital. He's the heart-throb of the Chelsea and Westminster!"
Hidden under a blanket
It was a little girl called Hadisa Husain who prompted doctors to set up the Facing the World charity.
She had a severe facial deformity.
Her medical condition meant her life was at risk, and suspicion about her appearance in her community in Kabul, Afghanistan had led to her being deemed 'evil' and condemned to be stoned to death.
She was just three months old when cranio-facial surgeon Martin Kelly first saw her in 1997.
Hasida Husain was set to be stoned to death
Her father had taken her to the hospital where a team of British surgeons including Mr Kelly were operating on children with conditions such as cleft palate, which Afghanistan doctors could not treat.
She was hidden under a blanket waiting at the back of the queue of patients when cranio-facial surgeon Martin Kelly first met her.
Hadisa had a 13cm gap between her eyes. She also had a complex facial cleft that involved the facial bones and skull, and left her brain exposed in the roof of her mouth.
Mr Kelly could not treat her then because there were not the facilities nor the assistance he needed, and he had to leave her behind.
Hadisa eventually came to the UK for her operation in 2001.
When she was back in Afghanistan, she wrote to doctors, saying: "I am in school now and very happy and I don't have any problems. I'll never forget you."
Sarah Driver-Jowitt, executive co-ordinator of Facing the World, said: "It was as a result of Hadisa that the doctors looked into this and found it was possible to bring kids over here for operations.
"In the first couple of years, the charity concentrated on making contact with hospitals and orphanages across the world to let them know we existed and could help."
Since 2003, 12 children have been brought to the UK for operations.
Each needs to be evaluated in their home country so doctors can decide if that child can be helped, and what specialist care they will need.
The charity then has to ensure the funding is available to fly them over.
When they are here, surgeons donate their time for free, and contributions from private individuals are used to pay for the cost of accommodation and hospital stays.
Ms Driver-Jowitt said: "One of the challenges is to say plastic surgery isn't just about appearance. These children have sometimes life-threatening and always life-limiting conditions.
"Over the three to five months they are with us, they are transformed."
Norman Waterhouse, who is based at the Chelsea and Westminster Hospital, said: "Martin and I went abroad to work quite often, and every time there was this horrific process where we had to assess whether or not we could and then say we could help this child but not that."
He said he was conscious he and colleagues were being entrusted with the care of children who were a long way from home.
"There isn't a single time when we don't feel responsibility and anxiety.
"But when it all goes well, there's an enormous sense of gratification."
He said the charity had long-term and wide-reaching ambitions.
"We want children around the world to be able to access regional centres, in countries nearer to where they live, where they can have the surgery they need."