Welcome to the forums.....
There's a few of us this side of the pond, but as you know places can be poles apart even if not actually that distant, hence it depends where you are.
The US contingent here are a good bunch but they also have access to a much larger market, so stuff like finding good varietal honey is easier for them. We have to make do a fair amount.
It's not impossible though. There's a few equivalents for some materials etc.
As for the ginger thing ? I'm also intending to try WVMJ's extraction method next time too as using just grated/sliced or whatever ginger can make for a lot of sediment thats hard to work with.
Don't worry about mega accuracy either, honey and yeast have a habit of unpredictability. There's plenty of info kicking around so you can work out whats going on and you can use real time measurements to know where you're at.
Apparently the hottest part of the ginger roots are just below the skin so I'd suggest just scrubbing any dirt off and the using the rest sliced or grated for the "ginger tea" extract.
For "energiser" tronozymol is an easy equivalent and for nutrient, youngs yeast nutrient is only 2 components, both are, as I understand, inorganic nitrogen sources hence it can be used vice pure DAP/di-ammonium phosphate.
Keep this updated though, it'd be interesting to read of what you settle on finally.
Oh and I prefer K1v1116 or D21 for meads (harder to find/get D21).