I've found with CMS5 that I am getting errors when trying to copy and paste a page. This seems to be because of the start publish date. If the date is set to '2008-07-24 12:30' I get the following error:
Can't copy page, because: "07/24/2008 12:30:00" is not a valid value for "Start publish"
I've tried setting the databse user's default langage to both English and British English, but neither seem to have an effect.
Would you recommend installing SP2 over the site to rectify this?
And would this mean us changing the license.config file at all?
Yes, you should upgrade to SP2. It's always great to include the latest bugfixes etc in your site :)
You do not need to change your license.config. The license file is good for CMS 5.X solutions.