Have you considered getting a PT/INR monitor? They're not cheap, but even just going to a clinic that has one will mean that you get your result very quickly.

In the UK, edoxaban has more or less replaced Warfarin, and has far fewer side effects or need for monitoring (or so says my GP).

I have mechanical bits in my ticker and so I’ll pretty much the last cohort to be able to jump, but your post prompted me to read up on Edoxaban and I’m apprehensively exited :)

Of course. I have atrial fibrillation and it is more or less standard medication for that in the UK (along with god knows how much other stuff). My (late) Dad had the same problems as me, and he was never confident he had taken the right amount of warfarin. But if you have heart valves, stents or whatever, or indeed anything, please don't take this as medical advice - IANAD.