I balanced the system the first rad on the system to heat up is in our sons bedroom I opened both valves a quarter turn, the next rad to heat up is our bedroom I opened both the valves half turn and so on until I got to the last rad to heat up which is in the hall and I opened it fully both sides and its that rad that does not heat up.
I'm sorry to say that your system is not properly balanced. How far away the rad is from the pump is only part of the story, the size of the rad is also relevant.
Here's a quick method, which will give reasonable results.
Remove TRV head and set valve at opposite end to one-third turn open.
On the other rads:
Identify which side of each rad is the hotter and set the valve fully open; set the valve at the opposite end one-third of a turn open. If you find that the LS cap is on the 'hot' end, you will probably be able to just swap the cap with the wheel head at the other end.
Set the pump to constant pressure by turning pump knob to the
right and raise the pressure (the 'm' setting) until the last rad is warm.
Let the system warm up and temperatures stabilize.
Repeat the following for all rads until you are satisfied
Feel the return (cooler) pipe on each rad and compare it to the last rad. If the return is warmer, close the LS valve by a very small amount; if it's cooler, open by a very small amount. You will find that the temperature of the last rad changes as you alter the earlier rads in the change. The amount of change you should make is minimal.
Let the system temperatures stabilize.
Recheck the pump setting - you may be able to lower the pressure.
End of repeat
Replace TRV head and set to required setting.
Set the wheel valves (hotter side) of all other rads as required.
What side on the red turn knob on the pump do i need to adjust left or right hand side
When you have finished balancing the system, turn the knob to the
left and set the pressure to the value you had when balancing was finished.
NOTE
For balancing you turn the knob to the
right to set the pressure; when the system is running you turn it to the
left to set the pressure.