Getting to the Avish
It's easy enough ... when you know where it is.  Usually we arrange to meet visitors beforehand in the village of Drumahoe and drive them up. 

The Avish Cottage
Avish Lane
38, Kilnappy Road
Campsie
Co Derry BT473LG    

The red arrow marks where you turn off the Kilnappy Road and onto the lane leading up to the cottage ...  At the bottom of the lane, we've placed a blue wooden sign saying 38/40 (for 38 Kilnappy Road is off rather than on the Kilnappy Road).

From Belfast International Airport approximately 62 miles, 1 hour 20 minutes travel time.  M2 - A6

From Belfast City Airport approximately 75 miles, 1 hour 35 minutes travel time.  M3 - M2 - A6

From Dublin Airport  approximately 150 miles, 3h20mn travel time.  M3 - M2 - A6 - M1 - N2 - M2 - M22 - A6

Take the A6 from Belfast to Derry/Londonderry.  In the village of Drumahoe, take the 1st road to the right, then 3rd right at Faughan Reformed Presbyterian Church, onto the Fincairn Road. At the end of this windy road, which rises steeply at one point, turn right, then almost immediately left, just before two adjacent cottages, into a narrow lane.  (The Avish Lane is just above the marker on the Google map.)  Our cottage is at the top of this tarred lane.  Take the second entrance to the right, just past the cottage, to enter the courtyard.

For those equipped with GPS, the postcode of the cottage is BT473LG