AN ambitious project to give 300 severely mentally handicapped children a ''home away from home'' is to be launched tomorrow. Most of the children suffer from cerebral palsy and all are patients of the Caritas Medical Centre in Shamshuipo, where many attend Lok Yan School, the only hospital-based educational facility for severely mentally handicapped children in Hongkong. Operation Sunshine needs between $5 million and $6 million to equip an entire block within the compound of the medical centre. Lady Ford who chairs the fund-raising committee, said the plan was to provide the children with bedrooms, instead of wards. ''There will be 16 to a room, four to a niche in colour co-ordinated islands, with brightly painted beds, lockers, matching curtains and splashes of colour everywhere. As much as possible, we want to make the rooms like home, remembering of course that we must have their isolation units, oxygen tanks and other emergency needs,'' she said. Until now the mentally handicapped have merely been kept clean and fed. It was now recognised that they had to be trained. ''The big problem is the attitude of the public. We are fighting to show the parents of these children that we understand the need to educate them to the best of their personal ability. ''If we can create a completely different atmosphere, it will be less distressing for parents who have to leave their children there,'' she said. Lady Ford did not want to downgrade the good work done by the Hospital Authority ''under really difficult circumstances'' but conceded that conditions of the children in the wards could be improved. Children at the centre are housed 50 to a ward, with two nurses to look after them. Their wards share the same floor of the building at the centre as the Lok Yan School. After each school day, the children revert to being patients. Lok Yan headmaster Mr Pun Hung-wai complained his pupils received no stimulation once they went across the corridor into the domain of the Hospital Authority. Children who, half an hour earlier, were learning toilet training and were being encouraged to use their limbs, were tied to beds. Lady Ford, who works as a volunteer at Caritas, said lack of staff was a problem, particularly in Hongkong where there was a general shortage of nurses. Before he left Hongkong, former governor Lord Wilson visited the Caritas Medical Centre and was so moved by the plight of the children there, he approved a $10 million grant from the MacLehose Fund to improve conditions. That sum has covered the reconstruction of the abandoned block in the compound and for a covered walkway to connect it with the school. The remaining $6 million is being sought through the public appeal to be launched tomorrow. The Operation Sunshine appeal will end on May 29 with a fund-raising concert at the Coliseum and will feature top Hongkong singers Alan Tam, Sally Yeh and child star Siu Pak-lam.