What height should the vacuum point be off the floor

Aussie Vac recommend that the inlet valve (vacuum point) are commonly installed at the same height as electrical power points. 

The centre on the inlet valve should be in line with the centre of the power point. 
Otherwise, the centre of the inlet valve should be 300mm from the bottom of the floor.  

If you have high skirting boards, you may need to reassess the height of the inlet valve.