Help Please? Clothes for a funeral?

I'm attending my grandmother's funeral next week, and as she loved bright colours, it is not necessary to wear black. I don't want to wear anything too bright though, for obvious reasons. Does anyone know of any UK shops that might sell a wide range of plain dresses all in one colour? I don't think a pattered dress would be appropriate :/ but everywhere i've looked is just stocking poolside floral things. I want to look my best because this is a very important day, obviously. thankyou x