Yeah the heat, Gaz in really cold weather advise your friend to pre-heat the water in the tank for about an hour or so before he starts work, it'll be pipeing hot then! In terms of cleaning, put it this way, I could run the cold pump and clean with cold water, but I don't, I'll leave it you you to work out why.
I make a point of showing customers my system and explaining how it works. It looks the business and justifies my prices, taking time to explain all apects of the service is a great way to get customers to choose my service even before I've told them the price. If all you tell them is the price, its a yes or no answer.
John