Tried everything that I can think of.
If I turn off all the rads and then turn one of the upstairs rads on
it will heat up OK but if I try to increase the number turned on the
the heat is greatly reduced and infact only a few rads get the heat at
all, I know it at first seems like a balancing job, but surely an
Ideal mexico super 3 60000btu boile can deal with a few rads
upstairs..

I live in a 1965 4 bed detached house with 4 doownstairs rads and 6
upstairs rads. open system CH. Measuring the pipe temps on the
furthest rad ( single) when turned on by itself gave a reading of
inflow=125F , out flow=101Fr both valves set fully opened.

Is it possible to add a 2nd pump to the system to boost the water
circulation speed is necessary..

... Tony