Ibiza is a wonderful place to go off-season and the Germans know it - they enjoy year-round direct flights. So it is galling that Ryanair withdrew its direct UK flights to Ibiza in winter 2011 after the Ibiza government withdrew its subsidy.
However all is not lost. It is possible to fly there on a variety of routes including London to Madrid to Ibiza; London to Majorca to Ibiza; and London to Barcelona to Ibiza plus routes via Germany.
Be prepared to spend most of a day flying. However we've discovered some good routes with quite civilized flying times and at reasonable cost. Easyjet, Ryanair and Spanair are all worth checking. The site edreams is good for internal Spanish connecting flights. Watch out though as it charges a £20 administration fee unless you use a prepaid Mastercard credit card.
As a rental property owner in Ibiza we would love to go more often to stay in winter but the lack of direct flights has been a hindrance.