I think you ought to go through the whole of the wiring if it has been done by the heating "engineer".
There are apparently three two port valves in this system.
Each valve normally has a grey wire and an orange wire connected to a built in microswitch.
All three greys are connected together and are connected to permanent live.
All three orange wires are also connected together and go to the boiler switched live terminal.
A permanent live, from the same source as the grey wires are connected to, goes to the permanent live terminal of the boiler.
A neutral also goes to the boiler as well, of course.
The pump should connected, live and neutral, to the appropriate terminals in the boiler.
So, there should be a four core flex going to the boiler from the wiring box that the valves are connected to, and a three core flex coming from the boiler to the pump.