I opened up the laptop and carefully took out the right fan (carefully following instructions from ifixit).

I cleaned the fan as best I could with blower and tweezers and carefully reconnected everything.

I switched the laptop on with the bottom casing still off and could see both fans working okay so switched off again and closed it up.

MacsFanControl said both were now running (whereas before right fan constantly at 0rpm) and after some tests it's clear the kernal_task issue is no more and I'm running both monitors, 6 USB devices and processing heavy software and not even at half load.

Glad I tried the above before purchasing any parts or anything like that!

I opened up the laptop and carefully took out the right fan (following instructions from ifixit).

I cleaned the fan as best I could with blower and tweezers and carefully reconnected everything.

I switched the laptop on with the bottom casing still off and could see both fans working okay so switched off again and closed it up.

After booting it up MacsFanControl said both were now running (whereas before right fan constantly at 0rpm) and after some tests it's clear the kernal_task issue is no more and I'm running both monitors, 6 USB devices and processing heavy software and not even at half load.

Glad I tried the above before purchasing any parts or anything like that! It's 24 hours later now been throwing video rendering, gaming, three screens and more at it - and no problems whatsoever.