Unless your carpet cleaning is going to border on the obsessive, I think this is one piece of gear it's worth hiring every 4-6 or more months, rather than buying. 15 quid for a 24hour hire including one lot of consumables (enough for 4-5 rooms) seems to be the going rate - prolly more in Landan, mind ;-) The hired-out kit tends to be of a better spec, though obviously more bashed about, than what you'd buy at an affordable retail rate.
Just an idea... Stefek