Business rates explained to a foreign investor

[windy]

Hello, I am trying to calculate if there is any point in expanding our business to UK.
Now it seems it comes down to understanding the mystical business rate.

If we need to build a property that will cost 1 Million Pounds in total (land and building) and the multiplier is 0.46/7/8/9, what does this mean on the average in practice in percentage?
I studied one example here https://www.gov.uk/calculate-your-business-rates about Barbara the business owner. Her company owns a business property worth 10 000 pounds.
Her annual business rate is 4666 Pounds.

So if our building project costs around 1Million, will our real estate tax be closer to 50%=500 000 pounds annually?!?
Is this real?

Since the tax rate is estimated by the local council, what if they say "Yes it cost you 1mil to build it but we think you can now sell it for 2million", then is the business rate going to be 1 Million annually?

Same question if we buy an existing building for 1M Pounds?

Sorry to say, the whole system is extremely complicated if you have no exact location in mind (which is impossible until you have a budget) and very expensive (one in third council decision is challenged).

Thank you in advance for any help.