Prespray with pure clean or any quality prespray then rinse with Chemspec F90 liquid diluted to the appropriate strength as per the carpet & soil conditions.
Scrub with a rotary and extract with any high end portable.
In my opinion that's this topic simply answered
when starting a new business this is the last thing you need to be sorting out..... hows your website coming along? What marketing have you got in place? Don't get hung up about self neutralising, drying times etc at the start these things are not important.
Just searched 'Sevenoaks carpet cleaners' and you have a lot of competition how are you going to get your share of the available work?