I have a standard boiler 3way valve and pumped system. Up stairs 4 rads all working fine, down stairs I have three cold rads. Pump sounds like its working

A control/zone valve is probably not allowing the hot water to flow through the down stairs radiators.

What is a control/zone

A control for the system is probably defective.

OR
A zone valve is defective.

Since I do not know what controls the flow of hot water to your down stairs radiators I took a guess at what you have.

If the 3 way valve is controlling the flow then I would look to see why it is not allowing the flow to the area having the problem.