Hi,
Good quality pictures are what's needed to give an accurate appraisal, but what series is it?, what calibre?, any extras? i.e. barrels, box/case, accessories...all of this will have a bearing on its value.
To give you some idea though, a few months back I sold a 3rd series, .22, with tool marks, one missing screw, one non original screw and worn original finish for £250 (plus post).
HTH,
Dave