From my experience theyre not up to much. Ive got a Black & Decker one and after approx 18hrs of charging it lasts 6 minutes! Even the Dyson cordless hoover only lasts 4 minutes and its around £150.
There might be something else out there so good luck
Dont get a Dyson cordless - overated overpriced wouldnt suck the skin of a rice pudding absolute $%ite, it only lasts a few minutes and is too bulky to allow you to get close to nooks and crannies. Good marketing though !