clio 197 misfire diagnosis

I have a 197 and I'm struggling to diagnose the problem. It was misfiring at 2500rpm if you accelerated by say no more than half throttle, but is now doing it at idle as well, but stops as you accelerate until 2500ish rpm, misfiring then running normally further up the revs. If you accelerate full throttle no misfire? Fault code shows up as "DF119 CAMSHAFT SENSOR SIGNAL, camshaft tooth event." Timing belt kit has just been fitted as well as a solenoid on the top of the cam cover to the left of the engine. Any help is appreciated.
 
It might be the faulty camshaft sensor or they might missed the timing if the belt hasn't been installed properly.
 
Yep, as above. Could be timing is out or the camshaft sensor is faulty.

Who fitted the belt etc?