Hi everyone, my car has been suffering from starting issues, usually takes 3 times to get it to start and stay running, and a bit of a rough idle / drop in revs randomly. 

I have gone through a lot of things that I thought could be the cause 

I have changed the brake servo, servo vacuum pipe, throttle body, egr valve, spark plugs, pipe to the airbox, and the alternator but nothing has as of yet found the issue, it’s been smoke tested the only place which had smoke leaking out was the egr valve which is why that got replaced also but the problem still occurs 

any help would be appreciated as it’s an ongoing mystery 

Assuming it's the 1.8 petrol, remove the injector rail and replace the seals on the injectors.  I suspect you'll find one or more completely flat and no longer sealing properly.