To think a size 6 is not Medium?

[TheMagicTorch]

Following lots of recommendations on MN I ordered a pair of Mint Velvet black leggings. Ordered from House of Fraser and opted for a medium. Reviews online said these were great for a size 12. And a size 14 would be large. So I went for medium as I'm between a 10 and a 12 at the moment.

Opened them this morning and the outer tag says Mint Velvet M LG Black Straight Legging but they looked tiny - even just holding them up I could see they would be too small.
The inside tag is a New Look tag sized UK6.

Is this an error by House of Fraser or am I just totally ordering the wrong size here. Anyone else wear Mint Velvet and can advise?

I live and die in mint velvet and I buy size small (I'm 8-10) - I'd also suggest that they sent the wrong ones!

Huge price difference too between NL and MV, so don't let yourself be ripped off.