It is discriminatory in the sense that it is not the holy matrimony model and visa versa.
That it isn't your model doesn't make it discriminatory - you can still get married in that particular understanding of the traditional fashion in the sexuality neutral understanding, it doesn't exclude you (although your own sense of entitlement might, but that would be on you). The 'holy matrimony' model, on the other hand, excludes people based on their sexuality, that IS discriminatory.
As the law stands in the UK people involved in wedding can opt only to deliver the holy matrimony model.
Yes, the law as it stands is not entirely sexuality-neutral in that it gives certain providers the choice to discriminate.
I think people have been arguing that the holy matrimonial model be scrapped.
No, in the main I think people have been arguing that the law is fine; some people, both within and outside of these religious traditions have been balancing their take on the principles espoused by the religion against the doctrine and finding the doctrine wanting. They don't want to scrap the 'holy matrimony' model they want to update, adapt or adjust it to be more inclusive. Others want to keep homosexuality out of their sacred space - that's what the modern definition of homophobia that you were railing against is, it's the deliberate differentiation of treatment of people based upon their sexuality in a manner that is not justified. Your particular interpretation of scripture might consider it justified - others disagree.
This makes it seem that the gender neutral model has been the preeminent universal model for marriage and then along come pesky man/woman model supporters and holy matrimony model supporters and chuck in meaningless terms like holy.
It does nothing of the sort, it acknowledges that marriage, and the cultural corollaries of it in other cultures, have occurred in a range of forms and fashions over time, and that Christianity in general doesn't have a proprietary claim to it, let alone a particular sect, cult or take from within Christianity. People haven't suddenly started throwing in terms like holy, they've been in use for a considerable time, but they are meaningless concepts that are just there to try to insulate a claim or argument from enquiry - if you can make something sacred you can remove it from the realm of rational discourse.
That is complete 180 degree revisionism with the gender neutral model actually being the recent addition.
Ancient Greece called and wants to talk to you about the sequence of events here. After they've finished, the Polynesians, Chinese and a few of the African cultures would like a word, too.
Effectively you’ve started your post as a reasonable pragmatic posing the question why can all models not just exist together and ended as just another person who sees no point in the existence of other models also the word holy is not included for cosmetic reasons as you seem to suggest.
It's not that I don't see that they can't coexist, it's just that I don't see any heterosexual couple's desire to have the heterosexual ceremony overseen by a religious figure of their choosing is in any way incompatible with the next couple, who happen to be homosexual, having their ceremony overseen by a religious figure of their choosing. I get that individual religious figures might have an objection, but I don't see that it isn't homophobia and perfectly acceptable to point that out.
If you are religiously homophobic the law, currently, permits you to discriminate on those grounds, the Equalities Act conflates religious belief with traits like inherent traits like ethnicity or sexuality, and sets it up as some sort of differentiated philosophy; I think that's wrong, but it is the current situation and it's not likely to change in the short term.
O.