I have mixed feelings about Winter Heliotrope (Petasites fragrans) which was probably introduced to the UK as a garden plant. It originates in North Africa and/or the Mediterranean depending which reference book you read. It's clearly very hardy, spreads rampantly by rhizomes, is semi-evergreen and flowers early.
 Invasive plants have their merits but the flowering is usually rather sparse and there are plenty of other ground cover plants I would favour for their foliage. It's certainly persistent; any piece of rhizome in the soil will sprout anew and multiply. Thus Winter Heliotrope has become a widespread garden escape, I see patches of it all over the place. 
 I should note however that the flowers do have a deliciously fresh scent of vanilla and chopped almonds!

 [Postscript. Despite my mixed feelings I would also add that this colony of P. fragrans has somewhat modified my view of its habits. It is flowerier here than when I have seen it elsewhere and the leaves bigger and healthier. Perhaps this spot suits it although it is said to be a plant of damp shady environs.]