Any advice for diagnosing in UK? Or just keep going. On and on and on ...

I've got all the symptoms of some sort of mast cell disorder. Anaphylaxis and shock for 3 years now. Ongoing allergy tests (that are moving VERY slowly on NHS) show only allergy to dust mites (which if definitely NOT cause these repeat episodes

KIT test negative, baseline tryptase normal (though was 25 three days after one hospitalisation).

I have more allergy testing coming up but I just want some answers.

What tests should I request to rule out anything possible?

Is it worth going private, and if so, where??? I can travel anywhere in UK, but live far southwest. Nearest NHS specialist allergy clinic is Plymouth, which isn't very close to me in any case and they haven't been helpful either. They apparently ruled out mastocytosis but are now focussed on environmental and food allergies, which don't correspond to my episodes in any way.

What are my next steps? Three + years of random anaphylactic shock are doing my head in.