I would imagine a good portable vacuum with a powered brush would be far less work than a £15 carper sweeper.You might want to just get a 15 quid carpet sweeper off Amazon and give that a go. Basically it just seems like having a brush that attacks the carpet is better for hairs than a hoover, and it's a lot easier to get it out and give the carpet the once-over. If you're feeling lazy and fancy getting something to keep the cats on their toes, most robot cleaners work on the same principle
The problem with robot cleaners is that they don't do stairs.