I'll do a proper update in a thread, but in short:
Enter your postcode
here and you get a report page. Download the "Water quality report (PDF)"
In that report, here are the values:
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View attachment 73171
Magnesium is missing. I can't remember where I got it from, so just go with 15 for now.
mg / l is (for all of our purposes) the same as ppm (parts per million)
Hardness/alkalinity is more awkward, as different things measure it in different ways, but here is where to start.
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This is measure as the Calcium ions, but brewing sheets want it in a different form. I can't remember the numbers, but a rough starting point to convert to "Hardness as CACO3", you can multiply by 2.5 (I got this by working backwards from my existing values - I'll try to find the correct method later).
So "hardness as CACO3"would be roughly 234
If you need "hardness as HCO3-", you can multiply this number by 1.22 (I
think) to get hardness as HCO3 as ~285.
Hope that helps. If anyone else reading sees any errors, I'll gladly fix them as I did this a while ago for my water and may have made mistakes. I can never remember the carbonate conversion formula