Yes your ex partner would have committed an offence in making a false instrument in order that it maybe accepted as genuine, thereby causing harm to others and it should be reported to the police, your building society and the lenders, the difficulty may be in proving you did not sign the loan documents, who was the witness to your signature?
These will be secured loans the £20K loan is usually regulated by the consumer credit act unless the lender is the same as that which loaned the money for the purpose of buying the house, if your ex partner does not maintain the payments on these loans your joint property could be sold.
I suggest you do not delay but contact a solicitor as a matter of urgency.