Tenants moving out and have arrears, but can I impound their property?

Tenancy Types and Management

I have tenants who stopped paying their rent 5 weeks ago, they have not responded to my calls and letters, so today I visited the property and see that the tenants are in the process of moving out, some of their possessions are still in the house. My questions is: Can I remove some of their property in lieu of the rent arrears and damage they have done? There is a motorbike IN the property that I am thinking of taking and holding 'ransom' until they pay me what they owe.
I'm worried that if I don't move fast, they will be gone in the next day or 2.

Will I be breaking the law?

As far as I'm concerned they have already left the property as it is clearly not been inhabited for several days (maybe even weeks), so I think I have a right to enter it, but not sure legally?