V1B is wrong:
I have 250V at the junction of R7 and R8.
Plate = +249.9V !!!
Grid = 0V
Cathode = +3.12V
Ok. Back to this set of voltages. The only other thing I can think of that matches your results is that the 3.12V cathode voltage stated here is actually for V1A? Because no voltage drop between R7 & R8 would obviously indicate near zero current. So the thing to check is the ground connection of V1B cathode.