True enough Squeeks, this is PDS Cleaning - they've been in the business for many years and specialise in building good quality rounds by door to door canvassing, then when they've got a big enough list they sell it.
One of their canvassers approached me once, to see if I wanted his help building my franchisees work - he told me he canvassed five evenings a week covering an area about 20 miles in diameter, and over the years he'd canvassed up something like £30,000 per year for the company.
At their prices, it's perfectly feasible for a hardworking window cleaner to turnover £1,000/week plus.
Mind you, they're not cheap