1st time landlord needs some advice...

[shentodj]

When my father-in-law died, we decided to let out his house.
We are using an agents, but they haven't proved too useful.

Yesterday the tenants finally vacated the property owing approx £5k in back rent.
The agent has just emailed to say that:
a)the gas has been cut off.
b)the electricity has been cut off.
c)the front door lock has been changed by a company called Utility Warehouse.
d)Key Meters have been fitted for gas/electric.

The agent is going to chase this with Utility Warehouse, but I wanted to know:
1)As we own the house, how is it that someone can come along and change the locks? Can they do this? Surely it’s still our house?
2)Can the utilities fit Key Meters without contacting us? Again, we imagined that we (the landlords) would have to be contacted before this could happen?
3)We are now left with the matter of chasing our ex-tenant for the £4.6 he owes. Our agent (not much help) is saying we can’t do this as we don’t know his whereabouts since he vacated. This can’t be right can it? How do we go about recovering our unpaid rent from someone we can’t locate?

Thanks in advance,
Shentodj