Thankyou to all who offered many suggestions. I've been busy on other things of late but spent some time this morning elimating some other things.
Since my last post I've done the following;
Changed oil and filter, no different.
Monitored the ignition pattern, normal.
Monitored the coolant temp signal, responded fast and no glitches I could see.
Checked compression cold, quickly stopped and tested again when running poorly and again when hot, all were near 1200kPa and very even
Blocked off EGR
Disconected and blocked canister purge line
Fitted new plugs.
Checked fuel pressure at 310kPa and flow seemed ok, no bubbles.

I haven't had a repeat of the injectors staying on and maybe it is a separate issue such as a chaffed ECU controlled return shorting to ground?

The only other thing would be to have the injectors checked but I'm doubtfull.

I'm inclinded to agree with some of the comments that it's a hydraulic tappet problem that this engine is known for. So a couple of questions for those that have done the job;

Can they be replaced without having to take the head off, ie remove cams and change?
I beleive the replacement ones are for the later 2.2 engine?
Can this problem manifest itself after some 130,000km that this car has now done?
Looking into the inlet cam box from the filler cap hole it looks very clean, again is that part of the picture?
This car will start perfect and then only develops the issue after say 2 to 3 mins of running for about 2 mins and then is ok as is when hot starting, again does this fit with your experience?
I asked the local Pug dealer re the issue in the hope of reading a tech bulletin on it but they denied all knowledge. Unfortunately my "mole" in the workshop is on holidays at present!
This car's problems is a first for me hence my protracted elimination, other 2.0 petrols in 206 and other 307 have been fine for me anyway.

Thanks again for your input to date and hopefully I'll have good news soon!