The ones I can find seem to be in dark colours like this one that I've tried:

http://www.monsoon.co.uk/Day-D.....artdresses

Or in prints that I'm not keen on:

http://www.boden.co.uk/en-GB/W.....Dress.html

I can see me trying one of those prints but they are 'very Boden' and as I already have a Boden print dress, I don't want to be type cast! The plain colours are again dark (black and purple).

How could I make the first black one feel summery? Or has anyone in the UK seen anything like this (I'd really like viscose as per Angie's recommendation) in more summery colours/prints? It can't be deep blue/navy either. Most things in my wardrobe are blue/navy - I've got to get something else!
Thanks!