so, there are very few cases of discrimination being brought on the basis of Gender Reassignment. There could be a number of reasons for that which include: the lack of discrimination taking place; the lack of access to justice for people suffering such discrimination.
If it was the second reason, presumably Stonewall have the financial resources and legal muscle to facilitate action/investigate barriers but have decided not to.
Presumably, anyone looking at updating the law (obviously Maya makes a good proposal but I am now of the view that a short bc is not helpful to either side) to help avoid discrimination on the basis of Gender Reassignment would start by looking at some cases that have been brought and then if they are thin on the ground, then maybe investigate if there are any barriers to bringing claims? Maybe Stonewall could advise? Either there are few claims or Stonewall are refusing to help - maybe they could be asked to provide some concrete evidence that discrimination is taking place.