Right,
I was going nowhere with this and filed a bug with Apple.
After a couple of weeks they got back to me saying, very simply, that I should add "webkit-playsinline" to the video tag on the HTML, as well as adding the "allowsInlineMediaPlayback" property on the UIWebView.
So in the end, this is what it looks like:
HTML
<video id="player" width="480" height="320" webkit-playsinline>
Obj-C
webview.allowsInlineMediaPlayback = YES;
And all works just fine :)
Hope this helps someone, as it's virtually undocumented and the only place I could find a reference to "webkit-playsinline" was in the iAds reference, where it says: "iAds JS only".
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