New stove with a back boiler is not heating the raidators?
It depends on 1. Which system the back boiler is connected to. 2. Whether or not there is an operating water pump. In my own case, the stove back boiler is only connected to the hot water cylinder and thus I only get hot water from it and my set up is quite common - yours may be the same. However, one of the houses I had in the past had a back boiler connected to the central heating system but the pump had to be switched on for the hot water to reach the radiators.
If it is a pumped system, check if the pump is running. If not find a switch to turn it on.
If its set up correctly your radiators should get warm at least in about an hour.