Many thanks for this, I had adjusted the php.ini, but wasn't sure how the self contained installer environment was configured, presumably this the php-fpm setting?
My paths are slightly different.....
I cannot find php-settings.conf in my installer directory, but I found this (perhaps I'm using a newer version?)
php_value memory_limit 2048M
I've restarted the services via SutieCRM stack manager tool, I'm not sure how to check that the new settings have taken effect, but I will try the slow tasks again (importing and mass update) and see if they are any faster.