It is not known who is asking this question. Is it a Bank? Banks do not give educational loan just to the student alone. Educational Loans are given jointly to the student and his parent (normally father) and an independent guarantor or coobligation also is taken. In your case no such details are available. If the loan crosses Rs. 7.50 lakhs mortgage of the property also is taken.
If loan is jointly given, you may proceed against the joint account holder who may be father or mother. As suggested by other expert, you can file a suit for recovery.
However, effective steps are as follows:
1. Write a letter to the High Commissioner of India in UK giving full particulars of the defaulter, loan given, his present address, phone number in UK.
2. Write a letter to the Passport Authority about the default, duly giving details of loan and his present address.
3. If you know the details his present employer, you may report the matter to such employer also requesting their help to recover the dues.