Scented soap. They have even been known to swim round the U bend of a toilet to get to it in a bathroom if they smell it after you have enptied the bath.
Calais. They don't seem to have this sense of 'fairness' towards vermin that Blair and co have.
Are you sure the tunnels don't lead under your house ? If not just pour petrol down and light.
They're faster than you are.
Put them down the tunnels to protect the rats then burn the lot of them.