Flying to Andalucia from the UK is easy as there are many airports, all within about 3 hours of each other, with a range of airlines servicing them.
British Airways, Easyjet and Ryanair all fly direct to Seville from the UK
British Airways, Easyjet, Ryanair, Aer Lingus, Vueling, TUI, Flybe and Jet2 all fly direct to Malaga from the UK
British Airways and Easyjet both fly direct to Granada
Prices do vary a lot, depending on the time of year and especially around peak holiday times in Andalucia. For example, flying to Seville around Semana Santa during Easter or Feria in May, would set you back a lot more than at other times.