Tenant may have moved out without letting me know

Just to update on this.

I went down yesterday and there's nothing serious to deal with. It's all cosmetic and nothing that a lick of paint and new wooden floors won't put right. The garden is in a bit of state, but again nothing that some hard work won't put right.

There's the question of utility bills now to deal with. There are letters there, addressed to the tenant, from Bord Gais (I assume this is the electricity) and another from Eir. I need to alert these that the tenant has moved out without notifying me, and I assume it's the same for them. Is it OK for me to open these letters and get the account number, or do I just call Bord Gais and Eir, give them the property address, let them know that I'm the landlord and tell them that the tenant has moved out and get the bills (temporarily) moved into my name while I'm doing up the property?
 
I would not open post addressed to another person, return it marked gone away, no longer at this address and have the meter put into your name.
 
Ring up both utilities and ask. They will usually open a new account in your name and close off the old one. You can take the money out of their deposits, hopefully.