Hello Again,
I have changed the max script size to 500M and just to be sure I also changed the max execution time but neither of these worked.
I reset the sitemap generator completly and began another sitemap generation, it got to around the same as last time which I estimate to be around 85,000 pages. This certainly seems like a max execution time or max script size but surely 500M and 50000s execution time would be enough?
This has definatly come with the new update to v2.6 as I never encountered this problem with the previous version and unfortunatly I cannot get hold of v2.4 again.

Any suggestions?
Thanks