There are 35 million households in the uk, some wont spend £5 to have their conservatory roof cleaned, and the members of moneysavingexpert arent the ideal target market for earning any money out of.
That said if you could convince them that your method of cleaning was the best, prevented algae regrowth etc for the longest period of time etc etc. And load the price to drop close then Im sure that some of those tightwads would part with over £70 an hour to get their conservatory cleaned.
Mark