I have an "XR advanced vacuum cleaning robot" £160 from Amazon. Fair play to it, the bloody thing is fantastic. Wakes up at 6am every day, trundles around a carpeted room for 2 hours and genuinely keeps the carpets clean. The dust bucket needs emptying every other day and is normally full of Mutt hair and dust.
It may not be the most intelligent robot, but for the price I have no complaints at all.