Tenant declaring bankrupt

I am a Landlord letting to a husband & wife with 2 kids. They are just coming to the end of their initial 6 month AST and are wanting to stop on but have just advised me that they have been advised to declare bankrupt.

They tell me they previously had a house, sold up but were left with negative equity and are still paying it off. The husband is self employed so they tell me they cannot go down the iva route and bankruptcy is what they have been advised to do.

I am concerned for my property. With regard s electricity, would an electric company change the meter and not allow them any credit? If they declare bankrupt whilst renting my property is there any entry registered against the property? Is the property likely to be viewed as having a "black mark" against it for credit or any other purposes? The property is currently mortgage free but should I wish to borrow money against it in the future, I do not want to be prohibited by the acts of my tenants.

They have paid their rent relatively on time and with very few problems over the last 6 months. If the bankruptcy is not going to affect my property and I decide to let them stay on, should I ask them for a Guarantor?

Any advice you can offer would be gratefully received.