I wore dark blue velvet trousers from Lands End and a blue(mixed shades) embroidered coat from East for DD's wedding in December.
You could also look at Hampstead Bazaar (London, Bath and I expect Internet) I wore raspberry pink silk trousers and a patterned silk jacket from them 3 years ago for DD 3 's wedding in August.
WALL, provided a metallic pewter coat and trousers outfit 7 years ago for DD 1's wedding! Finally, look at Sahara or Box2 , although the latter may be too big for you as they start at size 14.
I agree you do have to look around and perhaps be more creative than traditional MOB or GMOB outfits. But actually Jacques Vert (always reliable) may also have what you are looking for.
It may be that the dark colours you are seeing are down to the time of year. Early Feb is perhaps just too early for the Spring/Summer ranges to be fully available.