Tenants left without paying heating bills

Rent Arrears

Hi,

My previous tenants (joint tenants) left without paying the heating bill which is substantial. They didn't respond to the emails from my agent so I'm considering going via small claims court to recover the money.

I have the following questions:

1. Do I need to write letter to both tenants or going just after one is enough?

2. As I don't have their current addresses (I don't think they live together anymore) I'm considering using one of those services to track the debtors. Am I looking at the right thing or there are other ways of doing that?

3. How much time do I have to chase that debt?

Thanks,
Lucas