Thanks again Ken, I host with a managed VPS at Digital Pacific in Australia.
Interestingly, I had to upgrade with Digital Pacific as the standard hosting and (then) business hosting didn't have the memory resources to run Moodle 2.5. I changed my plan three times so I have a VPS hosting package. No problems now... but much more expensive than anticipated - and Softaculous will install anything regardless of hosting packages - it is up to the end user (me) to do the homework first. Wish I had known this from the start. On the upside, Digital Pacific always get back to me within 1-2 hours of posting a support ticket!!!
I have 13 courses and just over 150 users at the moment.
More courses and users will be added in the next month so I want to upgrade before this happens.
When you backup a course, does it back up user restrictions as well? I wouldn't want to lose the 'state' that each user is up to within each course - all my courses require pass grades to see the next activity.
Thanks again to all for the comments and advice so far.