Having been in a smart white and blue paint finish for many years, G_PIGY has taken on a much more military green in recent months.
Air-Britain : Shorts Skyvan 3 Variant 100
However, I don't think it's an ex-Argentine aircraft - Google reveals their Skyvans has c/ns of 1887, 1888, 1889, 1890 and 1891. G-PIGY is c/n 1943, and it's previous history is a little vague, but is believed to be ex-Mauritanian AF
However, Hunting's other Skyvan, G-BVXW, was an ex-Argentine Navy aircraft