I'm not sure that I agree with much of what you have stated, very few people will havethe ability to build a business of that size in a totally labour intensive industry, not forgetting that if you are employing then you also have to supply vehicles and equipment, all of these things push up your overheads particularly in the domestic arena.
Employing people is expensive, on the other forum another guy detailed why he was several pounds more expensive on domestic work than the majority of window cleaners, basically you simply cannot compete purely on price, one man outfits will always be able to work cheaper (and still make good money) than the big firms that employ dozens of window cleaners.
So in that respect the domestic market will not change that much, big firms will not compete.
7000 domestic customers, 200 new ones a week???
You are almost talking about employing a new window cleaner every week, then he has to be trained, that alone will take a couple of months before he reaches a competant level.
I have employed a great many over the years, some may last a few years, others may only last a day, some you have to sack for incompetance, overseeing the work they do is also time consuming, if this isn't done they will screw you over and cut corners, leading to lost customers and so on.
7000 customers in two years?
if that is in a domestic market that is an average price of £23 per customer per month (£2,000,000 per year)
I'm sorry, but I don't believe your tale, and in the unlikely event you are on the up and up, very few will will get even remotely close to that.