Please can anyone advise me of the best way to travel from Madrid to Sitges. Thanks
Try the train-Sitges got an excellent rail link.
you cd fly: vueling.com is no-frills for one-way but you can book one way with iberia these days too I think and their flights start at 19 euros plus taxes.
train has the advantage that you don't have to go on from airport but takes a lot longer even including check-in time for flight etc. renfe.es is rail website.