UK Car Repair Questions? Ask a Mechanic for Answers ASAP
So the radio will work, but when you turn the lights on it will shut off?
If you just turn the key to the run position without starting, will it load fully and start working? There are two circuits, and a load reduction relay that cuts the accessories off when you start the car, then allows them to be repowered once it is in the run position.
It sounds to me more like the radio has died- either just a coincidence, or they did something when they were in there replacing the ignition. Did they just replace the mechanical portion of the barrel, or the ignition switch as well? There is a circuit built in there that should power the radio. Is the radio spliced into the wiring, or does it have a "plug and play" harness that hooks up to the stock radio harness?
They should be able to just plug the radio in and power it up as well, to see if it is operating properly.
If it still is, then you may need to check for power on the supply wire to the radio, and see if it cuts out after you turn the key to the run positiion