Thank you Austin!
There's a line missing in your code, around 130, above t_fine=var1+var2, which is in the original source:
var1 = ((((temp_raw>>3)-(dig_T1<<1)))*(dig_T2)) >> 11
With this in place, the python code works for me, and it's the only complete chunk of code I could find. Well done.
The Omega2 i2cdetect doesn't see the BME280, I believe i2cdetect is defective, but the rest of the i2c code works fine.