Having issues with clutch drag when engine warm.It would appear that the clutch hydraulics go a little spongy.Having looked at the plumbing of the clutch system it seems the cylinder and pipework inside the bellhousing wouldnt get bled from the external nipple.Any tips how to flush out old fluid and probable air/moisture.Was thinking of using a syringe and some thin pipe to poke done tube into the area of the slave cylinder ?

It could be a problem with the Dual Mass Flywheel

DMF normally knocks at idle if faulty. I once had a strange problem after replacing the clutch on an Audi , can't remember which one but I was unable to bleed the clutch , couldn't get any fluid through even when using a pressure bleeder, a vacuum bleeder and some pumping the clutch pedal all at the same time . After fitting a new master cylinder the problem was still there, after loads of head scratching I decided to disconnect the hose from the reservoir to the master cylinder and found the outlet from the reservoir was still sealed as you would find on a car with an auto transmission . opening the outlet allowed the clutch to be bleed easily. Had I not seen it myself I wouldn't have believed it!

Trouble with a lot of concentric slave cylinders when it cones to bleeding, is the nipples are on the inlet. It can help to pump the clutch pedal and then hold down (get an assistant to do that bit), give it a few seconds for any air to settle and then open the bleeder. The clutch will then push/squirt the fluid and hopefully any air out.

Having said that, dragging clutches are rarely just air in the slave if it's been working right before. More often bearing failure, diaphragm failure/finger wear or leaking slave (so bleeding may be a temp' fix).