Snug as a bug in a rug

As UB40 might say:

There's a rat in my compost and I don't know what to do!
There's a rat in my compost and I don't know what to do!

Before planting a half row of baby and rainbow mixed Nantes carrots yesterday evening I was forced to investigate my compost heap, after my plot neighbour informed me that he had a rat in his compost bin. Said rat had apparently been attracted by the warmth offered by a piece of carpet he had placed over his bin (in order to promote decomposition). He spotted that my palette compost bin also had a cosy covering of carpet and suggested that I might want to take a peek under it.

He was right - a homely little rat bunker had been constructed, complete with half-eaten carrots and oranges. The critter would be as snug as a bug in a rug, nestled in there. A good forking has now rid the bin of Roland's safe house, but I'm concerned about him coming back and the associated risks of rat urine and excremant. I'm going to have to do some anti-rat research.

Any suggestions would be welcome.