Thanks all for the replies. Just to add, at the weekend I took out my MAP sensor and it was long overdue a clean - in all honesty it does seem to run a bit better now, but it isn't where it should be. Higher revs still seem to have hesitation but it feels more pokey off the line now (or maybe its all psychological and I'm just living in hope)
I'll give the MAF a look at next (based on all the advice) as that seems to have been the cause in several cases. When it was replaced (old one went in the bin) it was reading 0 but the new one does read ok through the Nanocom, but as you all say, this doesn't necessarily mean it isn't the problem. I do have to admin that it isn't a genuine one, but rather a cheaper aftermarket MAF so all being said and done that could well be the cause.
New injector loom is in, hasn't made a difference but nice to get another job ticked off. ECU is still clean but will keep monitoring that for any residual oil that creeps that way over the coming weeks.
Fingers crossed it will be the MAF - Ill try disconnecting and running to see if there is any difference.
Again, thanks for all the helpful advice - nice to know I'm not the only one!