Thanks to everyone for their responses.

So the car doesn't do this from cold start or if you've done a decent journey only if the trip was really short and then it's left.

It may well be a fueling issue. Thats why my mechanic suggested focusing on the injectors next. Having the injectors serviced is about 1/5 the cost of a new set of OEM ones. The car I've noticed has started puffing out a cloud of noxious smelling visible gas on cold start that goes away quite quickly but it doesn't smell good. When you rev it once you're moving it doesn't out gas at all. I will ask my mechanic to check the high pressure fuel regulator to make sure its all good

The car seems like it has the softest of misfires still. The idle is rough but through a process of pain staking testing I've found the PCV diaphragm is perished. If you cover the little hole at the back of the valve cover it will make the idle rougher, as soon as you uncover the same hole it will hiss like anything. I've got the RKX kit to replace it. I will be doing the EVAP (purge valve at the same time as all the other gaskets.) Im wondering if the PCV is bad enough that it's causing a rough idle and for some oil burn on start up.

If it was the cam angle sensor would it not do it all the time? It cranks and starts fine 99.9% of the time.