The best way to get to the house is to fly to Trieste in northern Italy. Ryanair often have suite cheap flights from Stansted. You can also fly Easyjet to Ljubljana but I haven't done that. In Trieste airport you can hire a car. There are several companies there from Hertz, who offer a special deal for Ryanair travellers, to Eurocar, who I found to be the cheapest last time I was there.
The house is about 1 hour 15 minutes from Trieste and probably about 1 hour 45 minutes from Ljubljana.
CLICK HERE for the Ryanair website
CLICK HERE for Easyjet website
CLICK HERE for Europcar car hire
CLICK HERE for Hertz car hire