I took loan of GBP 4000 in 1996 & then left UK in 1997 without paying. I also used credit card & bank cheques for GBP 6000 but left UK without paying.
Are these debts erased from my identity now? Can I be prosecuted if I go to UK now?
It depends whether a CCJ (County Court Judgement) was obtained against you.
If it was not, and you have not acknowledged the debt (written a letter agreeing that you owe it, paid any part of it, verbally offered to pay it etc.) in the last 6 years then the debt is now past its statute of limitations and you can't be pursued for it. If a creditor does contact you and ask for repayment you can respond that the debt is statute-barred and they then cannot pursue you further.
On the other hand, if a CCJ was obtained against you then there is no statute of limitations and you can be pursued for the debt at any time.