It may well be an easy fix! It sometimes might require a replacement part, potentially a return visit. It may require a bit of rewiring if the cable is chewed, damaged, or we can't get to the faulty part. Sometimes we're able to isolate to faulty part if it isn't very important to you e.g a garden light that never gets used. We'll always try to keep the power on as best we can til the part is fixed. Sometimes, if the fix is outside our scope of service, we might recommend a service provider better suited to your needs to follow up behind us and complete the project.
The only real way of telling whether your electrics are completely safe is by having a thorough health check on the electrics (EICR) carried out by an experienced electrician. We specialise in these - please find out more here.