Figleaves do some nice stuff, some of it is really expensive. But they do every size you can imagine!
And Debenhams have launched a plus range, I haven't looked at it but I saw an ad when I went in there last time. They always have sales on, and I always stock up when they have a blue cross. I'm a 38F and they tend to have nicer stuff in my size than most places. But make sure you try the bras on, the sizes really vary across the different brands.
Jas x