I appear to need this IE specific meta tag in order to get IE8 to render my page in standards mode,
<meta http-equiv="X-UA-Compatible" content="IE=100" > <!-- IE8 mode -->
The site I’m working on is commonly available on what would be classed as intranet so I think that’s quite possibly why IE8 hasn’t been rendering it that way by default.
This seems a bit ugly to me but appears to be the solution.
Update: just fixed the first link.