I'm not a UK subject, so it's not my business, but I'd love to print out his letter, annotate it carefully and post it back to him:
'intersex' is not acceptable
'non-binary' is not a legal category
have you any evidence that gender non-conforming women have been having the issues you claim?
no trans person is 'barred from' essential services such as toilets - they choose not to use the available toilets designated for their sex.
women's rights to single-sex spaces are clearly in conflict with transwomen's demands to use women's toilets, which would make them mixed-sex spaces
does your British tradition of respecting the law exclude rulings of the UK Supreme Court?
the issues raised today were in fact raised during discussion of the Gender Recognition Bill in 2004, and several MPs made exactly the points that are made today: that sex is binary and it is impossible to change sex, making legislation based on 'gender' a nonsense.
and so on.
The Lords debate on the GRB is available at
Gender Recognition Bill [HL]: 29 Jan 2004: House of Lords debates - TheyWorkForYou
showing that there's nothing new about the kind of objections that GC women are making today.
Ed Davey became an MP in 1997, acc to google, so he was in the Commons when the GRB was being debated, and would have been aware of the strong objections coming from the Lords.