Thanks for your comments, advice etc, Walter and Keith, appreciate your help.

After some experimenting i've come to the following conclusion: Whenever working on the style Guitar Ballad this problem arises,
if I remove the mega voicing accompaniment parts, I presume it frees up memory and you can work on the style as normal, BUT! if you try and put back into the style any Mega voice parts from the onboard/original style, then you immediatly get memory full again.

The strange thing is though the Guitar Ballad style does not use all accompaniment parts (two are empty, phrase 1&2) but having said that, there are two Mega voices being used in the style.

Thanks again for your help,

Kind regards

Peter