That's a wierdo! Doesn't look like any of the usual British ones. I've checked all through Phillips and another book that has foreign ones and there was nothing like it. Are you sure its healthy? It doesn't look very well to me - does it need repotting? Have you had it long and was it always like that?Is it hardy?
Hope somebody knows the answer.

Yes, it's healthy, not at all pot bound & is hardy. I just bought it on Friday from my visit to Norfolk Cottage Garden Plants. I think I remember she said it turns to bronze but not sure when, she didn't know it's name either.

Perhaps one of the fancy Asplenium bulbiferum varieties or relatives?

I have found it:
Athyrium filix-femina ‘Victoriae’, the Victoria lady fern, was discovered in Scotland in 1861 in the midst of a feverish fern collecting era later dubbed the “Victorian Fen Craze”. At the time enthusiasts in the UK actively sought out unusual fern forms and this is indeed unusual! The pinnae criss-cross one another forming a series of letter x’s on the frond. In addition the tip is crested forming drooping tassels of split tips. Not surprisingly this cultivar attracts a tremendous amount of attention in the garden or container. The deciduous fronds reach from 1 to 2 feet in height and the plant needs light to full shade.

that's one to look out for. its very pretty.

There are 2 types, SBG, A. angustum (narrow lady fern) is the lacy one.

Goodness its very different from the usual lady fern isn't it?

Yes, Stera, it is & that's why it caught my eye, even when you look up criss cross fern you get varying results.

is that a fern that has been attacked by the dreaded lurgi?