Ford Mondeo not able to start

car was driving ok till i stopped started car drove off down kerb then the car died no power at all nothing worked RAC came out and said it had blown fuse in engine bay no 40 fuse kept no blowwing fuses as key is turned he said it may be the ingnition switch changed it and car started it i drove off my drive and it died again RAC came back out and go it started and suggested i change all the relays to do with the ingnition witch i did and car seems to be ok but now dont trust it could it be anything else that may cause this to happen