Hmmm....that serial (BZ890) was a Liberator III assigned to No. 178 Squadron from Sep. 1943 until Dec. 1944. No. 178 Squadron was operating out of Libya in 1943 and then later out of bases in Italy as the Allies advanced into that area. The color scheme does not match the Liberator colors schemes for No. 178 Sqn. in the Med (two-tone uppers, black below.) This one presents a mystery at the moment - perhaps Chris (through Mr. Pacyński) can shed further light on the matter.
Added later - BUT WAIT, there's more! This aircraft was apparently later assigned to No. 301 (Pomeranian) Polish Sqn. which operated both the Handley Page Halifax and the Liberator out of Brindisi, Italy and was involved in supply dropping to underground forces in Yugoslavia and surrounding areas from late 1944 until the unit returned to England in 1945. The
middle photo, eighth row shows GR-S (actually S/N BZ965) with the nose art of the model clearly displayed, as is the color scheme as presented on the model. The same website shows another aircraft wearing GR-S so it may be possible that BZ890 (if it was indeed transferred to 301 Sqn.) may have worn that code at one time.