Handicare have a great range of Bariatric solutions, and also offer a powered (self driven) mobile hoist capable of lifting 270kgs called the EVADRIVE600. This will be on display at the SYA roadshow.
This is a good alternative to an overhead system if either the building is unsuitable or the cost is prohibitive.
http://www.handicare.com or http://www.medix21.co.nz for further info.
Aaron
Medix21