Helleborus lividus subsp. corsicus (Introduced- USA/UK)

Helleborus lividus subsp. corsicus (Briq.) P.F.Yeo, Taxon 35: 157 1986. (syn: Helleborus argutifolius Viv.; Helleborus corsicus Willd. ex Mabille [Illegitimate]; Helleborus lividus var. serratifolius DC.; Helleborus trifolius subsp. corsicus Briq.; Helleborus trifolius var. serratifolius Gürke);
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Corse, Sardegna; Introduced into: Austria, France, Great Britain as per POWO;
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Ranunculaceae Week: Helleborus argutifolius cv Silver Lace from California:
Helleborus argutifolius Viv. cv. Silver Lace syn: Helleborus lividus subsp. corsicus (Willd.) Tutin; H. corsicus Willd.
Herbaceous plant with spinescent-dentate leaf segments which are usually three in number, paler green above; flowers up to 7 cm across, pale green or suffused with purple.
Photographed from SFO Botanical Garden in California in July, 2008.
Common name:  Corsican hellebore, the cultivar is known as Silver Lace

Ranunculaceae Week: Helleborus sp. for ID 050511MK1:
Please help to ID this Helleborus sp. I am not sure that this plant is found in (temperate) India. I photographed this at Cambridge city of UK on last week of March, 2011. Please resolve this ID.
.. indicated in earlier post that this resembles H. niger.

References:

Catalogue of life  POWO