When I run TestStandardGame I get 150fps whereas with HelloSimpleGame I get > 600fps.
Why is that?
StandardGame defaults to vertical sync. Is your refresh rate set to 150hz? 
If so, what kind of monitor are you running that gets a 150hz sync? :-o
I've got a 21" CRT that gets 150Hz refresh…it's stacked beside my 19" Widescreen LCD though (60Hz), but that 150Hz is crap in comparison.
I jumped to LCD quite early, so must have missed the higher refreshes. 
Changed Vertical Sync option to "NO" and now I get 1300fps.
I will read up on this subject as I don't have a clue.
Another point for StandardGame baby! 
Vertical Sync locks the update rate of your game to be synchronized with your monitor's refresh rate (how many times per second the pixels are redrawn on the screen). This can help keep screen tearing from occurring and generally offers a much smoother game flow. Further, it takes some of the load off your CPU since there's really no reason to have the updates occurring 1300 times per second it's just wasting CPU and then other aspects of the game aren't getting the power the need.
I'm a big fan of vertical sync and honestly don't know of any reason why it shouldn't be used by default in all games these days.
Presumably if I use Vertical Sync and my fps is locked at say 150fps then the wasted spare capacity can be used to run background threads?
Yep!