If you dont get the Sebo then a long handled carpet brush at about £18 will do the job.
Use it to brush the carpet prior to vacuum cleaning (and the Kirby is a really good tool for that),
if you use a prespray, use the brush to rub it all around (agitation)
and then to groom the carpet when you finished - make it look real smart.
Re prespray - John Kelly at Restormate, Newcastle (he posts on here) sells 1 litre bottles of Nemesis Super for less then a tenner and that will last you an awful long time.
Its not a dtergent and therefore will not leave sticky residue in the carpets, therefore leaving the carpets cleaner and healthier longer.
and yes there is more to carpet cleaning then most people think - and some of the guys on here like Doug Holloway (who is into chemistry in a big way) are very cleaver with it. Me - I just about hang on in there! - my talents lie elsewhere - just not found where yet!