aha, that was it. My 2nd hand leather pencil skirt!! and the M&S zippy one.
It is a fab dress. I have a Chloe wool one in a very similar shape (with a kind of cut-out panel at the back though - and bought in the sale I might add!!!) which I wore to my (sssshhhhhhh) 36th birthday party last year with electric blue tight opaques and sky-high Louboutins. Wasn't muttonish at all (she says, fingers crossed, realising it is too late now but tempted to go and check the photos for confirmation anyway...)