If at all possible, avoid agents. We also had to go abroad, didn't have anyone to look after our property and hired a very reputable local agent with a large national firm.
They stole 4 months rent, pocketed our tax return and left us with tax to pay on rental income that they had collected the following year.
The branch it transpired was a franchise and they went bust. They knew for about 5 months that they were going under and lied to us constantly that the rent had been transferred to our account, or that there had been a mistake at the bank, or that the manager was dealing with it and wasn't available or was out sick, etc.
When you're on the other side of the world, this can be extremely distressing so if you possibly can, get someone you know and trust to look after your property.
The next agent we hired after this disaster was equally as bad allowing tenants into the property without checking their faked references, the tenants subsequently lived in the house rent free for 6 months until we managed to secure a very expensive court order and bailiff's order to get them out.
I would never, ever use an agent again.