A creditor can issue a summons abroad. The Civil Procedure Rules part 6 and practice direction 6 and 6b deal with this.(posted 8499 days ago)There's no question of extradition or anything like that because you've not committed a criminal offence. I'm not sure exactly what would happen, I guess it would be transferred to your local court.
Like with shortfalls in the UK, most lenders seem reluctant to actually issue a summons anyway and tend to rely on the borrowers ignorance of their rights and the law and use threats to get them to pay up. The fact that you're not in the UK will give you a better chance.