The Abortion Act 1967 creates exemptions to an abortion ban codified in <digs through legislation.gov.uk> the Offences Against The Person Act 1861, which mentions only women.
So a man who became pregnant wouldn't be a criminal if he tried to self-abort, in theory. What one of us needs to do is test this: identify as a man and get a GRC, then get pregnant, then video herhimself taking illegally-obtained abortion pills and surrender herhimself to the police for arrest. We can all crowdfund a top-notch defence barrister to argue that a TM with a GRC can't be prosecuted under a law that explicitly mentions women because of the "for all purposes" clause and OATPA's abortion ban isn't one of the explicitly-listed exceptions. If that argument fails, it proves the FWS argument that sex in law refers to biology. If that argument is successful, it provides a means for every woman in the UK to decriminalise abortion for herself by getting a GRC so that she is legally a man.
I'd volunteer but I think I'll be too old to get pregnant in two years' time when the waiting period for a GRC ends. Anyone fancy taking one for the team?