Unidentified Butterfly at Le Port

Found today in the field a weakly flying small grey butterfly with uniformly unmarked charcoal grey upper side wing surfaces.   Best bet is the Small Blue, Cupido minimus especially the size and rather round hind wings,  but the colour is normally brown in this species. The underside wing markings are not quite right either, there appears to be an extra, slightly diffuse spot in the basal/discal area and another well defined spot in the sub-marginal band, if this is a female, as suggested by lack of blue scales on the upper side. Best bet is that this is a local variant of the Small Blue. Any ideas anyone?

New camera, click to enlarge.