Ok, the saga continues.
All attemps so far have not produced the desired result, laptop running at normal speed whilst plugged in to charger.
Something that I have also noticed if it helps anyone with some more ideas is that when the lappy is powered up on the charger, the charger will get very hot. Whilst the lappy is being charged and powered down the charger will stay cool. Also if it has been left to charge up and say has 50% charge then is powered up on the charger, then the laptop will slowly lose charge even though it is plugged in. Confused.com
