tried these values and they did not help - checked and they had taken effect - they show up if I spill a php config page.
memory_limit 1024M
max_execution_time 600
However, when I checked the sitemap generation execution time, it said 16 minutes, so Im wondering if the max execution variable still wasnt long enough.
Assuming thats seconds, I have changed it to 20 x 60 (20 minutes) = 1200
And I am just re-running the generator now.