deek

If your wires are fine, check the connectors on the central locking/alarm control unit. This can be found under the passenger seat and is susceptable to condensation causing corrosion on the terminals. This was the problem I had. Simply removing it and cleaning everything up had my locks working again inside 5 minutes.

Think you may have damaged valves when timing belt slipped. They may not be totaly bent but valve heads could be slightly off line due to valve to piston contact. This will result in the valves not sealing properly on their seats and letting cylinder pressure leak back out into induction tract (hence roaring noise). To confirm this without taking head off, suggest you find someone with a diesel engine compression tester. Good luck and hope I'm wrong, but sounds awfuly similar to my own problem. Is it returning poor mpg even though seems to run fine?

did you check thick wire from solenoid to brush pack on starter when you had it off? Bad for corroding and can appear ok but have no continuity. This will cause sympyoms you describe because solenoid earths through brushes.

sounds like a simple vacuum leak on the inlet manifold. check all hoses/connections to the inlet manifold, from the air flow meter to the head. alternatively it could be a build up of carbon/muck on the throttle body, not allowing the butterfly to fully close at idle(allowing more air into mainfold). this is easily remedied with some carb cleaner