Rear parking lights (side lights)

Roomster 2014 1.2 TSI.   Having trouble with one of my rear parking lights, It'll stop working , warning light comes up on dash, Take rear light assembly off, waggle the offending bulb in its socket, bulb lights up again, My question is, what type of bulb is it? bayonet cap or screw?, I  wiggle it about but it doesn't show any sign of wanting to come out, I don't want to force it without having a replacement to hand, does anybody know what type it is? owner's manual is crap