If any of them are going to be accurate, I would say that the BBC is most likely of the 4 to be accurate because it is scientifically based. What it does is measure whether your brain is feminine or masculine or somewhere in between.
The other 3 seem to be based on either stereotype or preconcieved prejudices.
EDIT: On the Gender Test I scored a 11 out of 14 on the Cross Gender Identity Portion and a 0 out of 12 on the "simply a crossdresser" section. But the test is based on out of date concepts.