A lot of questions which I will try to answer.
Our window cleaning does around £40k a year which I have built up from scratch, nothing bought, all gained myself by leaflets and recommendations over the last 7 years. There were staff but the hassle made me get rid hence why most of these (over 400 customers) have been moved from monthly to bi-monthly. this allowed me and the wife to keep most of the customers after we culled the lower end.
Who ever did the sums and said £700/week well something is wrong as most days we pull in £300 to £400. This is per day so equates to between £1500 and £2000 per week. Don't multiply that by 52 because we don't work 52 weeks per year.
What someone is buying here would be a complete business, not just some goodwill on customer names/addresses. It would be in someones best interest to take over the business name and telephone number. Most customers wouldn't even notice the change over if the person is competent. A lot of our customers we have never met because they are out at work, so with them all being payment on day if in, or send payment or pay internet you are not going to lose many if any, if you do a good job. So hence you are buying a business not hoping the stuff round builders bring in will still be with you next month, and is it priced correctly.
Why am I selling? Because I have static caravans which I rent out in Dorset and want to be nearer to deal with. Plus I am getting older and need to slow down a bit. We will not consider moving until I have a buyer for the business, so before someone fancies muscling into the area thinking there will be 400 customers begging for a window cleaner think on.
Also I appreciate that this is too much work for just one person to service, so it would need 2 people to buy it or one person with staff to work it. I'm currently working on various ideas and one of them will be to sell off some areas whilst keeping the business for sale but at a lower price.