It's a Short Sunderland. It was a maritime patrol aircraft, operated by the RAF's Coastal Command. They were mainly used for anti-submarine patrol over the Atlantic, although some served in the Mediterranean. Post-war, they would operate with the RAF until 1959, serving in Korea and the Berlin Airlift. They hung on later in the RNZAF, with some receiving conversions to civilian use. The Sunderland was, while slow, heavily armed with machine gun turrets. This may have led to it being nicknamed the "Flying Porcupine" by German pilots, although this may have been due to the radar antenna later models sported. In one case, a Sunderland survived being attacked by 8 German Ju-88s, although with heavy damage.

http://en.wikipedia.org/wiki/Short_Sunderland

Not sure which model, I think it's a mark III

The aircraft in the photo is N9029, a Sunderland Mk I of 230 Squadron, it looks like the same photograph is held by the Imperial War Museum:

[Short Sunderland Mark 1, N9029 'NM-V', of No. 230 Squadron RAF Detachment based at Scaramanga, Greece, in flight over the Greek islands. It was from this aircraft that Flight Lieutenant A Lywood, reported the Italian fleet movements leading to the Battle of Cape Matapan, while flying out of Scaramanga on 27-28 March 1941.] (http://www.iwm.org.uk/collections/item/object/205208733)

They have a couple of other pictures of same aircraft as well.

Great! Thank you both for your responses.