Dr Higgins said the service had received a record number of telephone calls - 8,000 - on the first day of the official clearing process which matches university applicants to vacant places.
In addition, 24,000 people had visited its website, available to candidates for the first time this year.
Dr Higgins said: "This gives the lie to the people who are saying that candidates will not come into clearing because they have been put off by tuition fees. They are inquiring very busily."
About 16 per cent of university applicants find their places through clearing. The main areas with vacancies are physics, chemistry and engineering.
Students who have accepted a firm offer are bound by contract to take it. So students who have done better than they expected cannot abandon a provisional offer and try for a better course or university.
UCAS advises those who have just missed their grades to ring the university or college immediately. Some may still be prepared to offer a place.