The most convenient airport is Preveza PVK, (Axtion). This is a newly refurbished facility with good access to the western mainland and south to the Island of Lefkada, just 40 minutes by road.
However, some 50 miles further north is the ferry port of Igeomenitsa. This port is the main ferry route across to Corfu, with the airport at Corfu Town. Flights from the UK and Europe to Corfu CFU are very frequent and from many smaller airports such as Leeds/Bradford, Dublin, Bristol, Edinburgh and Belfast etc. You could find it more convenient and cost effective to fly to Corfu late week. Maybe as others have done, you could stay and explore this lovely island for a couple of days, then jump on one of the very regular commuter ferries on the Sunday morning for the delightful short passage across to Igeomenitsa. With prior knowledge of your ferry time I arrange for my taxi company to have a taxi waiting at the ferry terminal for your arrival, all quite straightforward, just sit back and enjoy the scenic drive down to Lefkada.