Can I ask what damage the tenents did? Thousands of euros is not acceptable.
Firstly you should immediately contact your solicitor, take lot and lots of photos and try to find out where the tenents have moved to and/or work. This is not your fault, why should you have to pay?
The legal process could take quite a while though so it might be worth calling your mortage provider and explaining to them what has happened. Maybe your solicitor could draft a letter to them explaining what has happened, it might add some extra weight to your plee.
Your mortage provider may be willing to "help" you in some way by perhaps reducing your monthly payment (interest only for a few months) or taking a payment break.
Another option could be to ask them for a top-up to cover the cost of the repairs. This is far from ideal, but its better than having your house reposessed. Hopefully, if you suceed on the legal route you could pay the top-up back.
I'm sure others with more experience in this kind of thing will have other suggestions for you. Best of luck!