Cheers guys. So I found a 4x4 specialist locally who knew all about these models which was good.
Told him my story and he immediately asked if the replacement MAF was genuine or not - I said it probably wasn't as a local independent garage had done it and they don't usually use branded unless specially asked.
He's fitted a brand new Nissan one this morning and says its pulling loads better but we won't know if its sold the cold start issue until its sat for a good few hours (probably not till tomorrow morning really). I'll take it for a big run later and hopefully it won't judder. If it does I'm going to get the EGR valve cleaned.
It could be the suction control valves on the fuel pump which are a common fault on this model, but at high speed/revs (motorway) its been fine, its more around 2000RPM its an issue - plus once its warm enough not to stall it idles perfectly. I'd expect an SCV issue to idle really erratically.
Thanks for the tips - and btw yes it is a Renault engine in this I believe. Felt a bit duped when I found that out, although I will say my other car is a 2004 Megane Sports Tourer and thats fantastic!