Worth noting that the BMA (British Medical Association) is the trade union of UK doctors and medical students. They are not a professional body or licensing organisation with the power to discipline or remove doctors (that's the General Medical Council) and they have no power to change things directly regarding the running of hospitals, which is the power of each local authority's NHS trust.

As far as I can tell, all this means is that the BMA has made it its own policy to believe this gender nonsense, and they will now try to lobby the government to make this into legislation. The government's recent shelving of changes to the Gender Recognition Act 2004 demonstrates (to me at least) that this is not a current legislative priority, especially with the Bexit brouhaha currently reaching fever pitch, and discussions over whether the UK government does, in fact, intend to breach international law.

TL;DR - Nothing has changed at a legislative level, this is basically just means that another organisation agrees with Stonewall & Mermaids. However I imagine the medical union has considerably more weight than some random charity.