Timing belt question?? 1.5 dci Megane

I had my timing belt replaced few months ago on my 05 Megane 2 1.5 dci, after getting it done the car wouldn't start mechanic said it was primer bulb after fitting new one and 11 or so pumps started and ran fine for a month or so. Woke up to go till work and the car wouldn't start came up injection fault.. Mind you this is the first time ever coming up that fault! Got a mobile mechanic out and he replaced 4 glow plugs said that was the fault and also said injector 3,4 was faulty. Anyhow, ran ok for about another month or so and again but ever so often driving down a motorway it would show " check injection " but never effected the cars performance.. After a few days all of a sudden try to crank the car and no start takes several goes before it actually does. Take it to a so called Renault speciallist which connected it to the machine, egr position sensor at a fault, misfire In cylinder 2 and pressure rail fault. Mechanic said it's basically injector 3,4 and that's causing start up issues. Anyways got 3,4 injector replaced and coded then the car ran lumpy but after driving 10 mile car started to run fine though when i push my foot hard on accelerator in 3rd, 4th gear doing around 50,70mpj bang screen shows injection fault though if I slowly put my foot on the pedal no fault shows but still same fault in the mornings the car won't start. So far I've had tdc sensor replaced new primer bulb, timing kit, 2 injectors etc and still same problem. My question is could this stem from the timing kit/pump not being timed correctly causing starting problems and injection fault?? Any help or insight would be really appreciated as I've spent a fortune on this already.

Timing belt question?? 1.5 dci Megane