Agree on Dyson. Don't bother with anything else. We have crappy hard-to-vacuum carpets, with shedded hair which most other vacuums miss. It was fab! Our carpet was literally a different shade after the first vacuum!
When ours was under 5 year warranty, every salesperson who answered the phone knew everything about all their products, and was really nice. They don't hesitate to send out a repairperson asap, for any problem. We've now had it 10 years and it still works perfectly.
But Argos and other shops are always having Dyson trade-ins or cashback, so it's also worth it to upgrade soon after warranty expires.
We will definitely stick with Dyson.