I might be wrong but I still don't think they accept women in the Royal Marines, SBS or SAS regardless of whether they can complete the training or not (And I mean doing the Commando course and completing selection - I am not talking about Int or other ancillary roles. )
GI Jane is still a fiction in the British Military. Great film though! (Try not to digress about the cinemagraphic experience of GI Jane - it's a throwaway comment really and it wouldn't make my top ten)