Hmmmm, I don't think Wilkos really rates as being a quality supplier. It's ok for cheep branded seed, but I dont trust anything in the "Wilko" brand.
Dahlia seed packets are marked cactus, pompom, decorative, etc."
- that's like buying lettuce labled "green" or "curly", or tomatoes labeled "red" or "small"
I think it'll be a while before Wilko will appear in the RHS Plant Finder, as you say - You pays your money, and you takes your choice. Me - I like to go for quality.