What's the correlation between GCSE grades and A Level grades?

[Ligresa]

If you get a B (6) at GCSE is there any hope of an A in the same subject at A level?

I know it depends on many factors, but I am sure I have heard people on mumsnet talking about the link.

@Ligresa as this 2 year old thread has been resurrected, how did your DD do in the end? What subjects did she take for A level? What grades did she get?