Do you already own it, @smallshinybutton? I think the only hesitation might be its summer-y shape, rather than the colour. The actual Tilda dress in the same colour-way would be perfect for most weddings.
The Rah Rah dress you link would be ok if you can get a warmer layer over the sleeves. Maybe a furry or velvet coat slung over your shoulders? (And definitely thermal underpinnings.) Plus some beautiful Victorian looking lace up boots?