Sweet Violet description:
Blue flowers in late winter and the spring, over a spreading low mat of green foliage.
Slightly fragrant. The fragrance of Sweet Violet contains Ionine, which has the power to deaden the smell receptors once it has been sniffed. 
A pollinator friendly plant including bees.
This is a butterfly friendly plant.
How easy is it to grow:
Good for the front of a border or in a wildlife garden and it is very easy to grow in most soils, including heavy or clay ones.
We have plenty more mail order wildflowers that are easy like this one.
Other common names: English Violet, Garden violet, March Violet or Sweet Pansy.
Botanical name: Viola odorata
The best position in the garden:
Sun or semi shade.
Is it useful as a ground cover plant?
Yes, it will keep spreading and is excellent for growing under trees.
What type of soil:
Any reasonable soil, also tolerates a chalky soil, and an acidic soil and a clay soil.
How much moisture:
Hardiness and, or, lifespan:
Care and maintenance:
When newly planted always keep it watered until the roots have grown down and it is able to find its own moisture.
Size of plant:
Height 10 cm.
Planting density – to calculate how many plants are required in a planting scheme:
Allow 4 plants per square metre, but it will continue to spread!
Reference:  Plantlife
Wildflowers by post, also herbs and other plants from this website.