Richard seems to get it dont know why others dont.
Imagine this situation.
Customer calls, im out doing something so they leave a message. They leave the phone number their never availiable on, so it might take a few days to a week to reach them. By then they have gone with someone else even though it was my leaflet that prompted them to get a window cleaner.
This situation and many others is now a thing of the past. EVERY incoming sales call gets answered not missed and I dont have to be glued to my seat.
In building my business I have come up with systems and methods that remove myself as I restricting factor in growth and turnover. Our process is more and more automated.
You can always have a call diversion to your mobile 
I have all my calls diverted to my mobile.
Last year had a leafleter to drop leaflets for me, he would do it from day to day basis and do 1k a day. I was at that time cleaning windows.
Even thought its ONLY 1k a day, i would get pis*** off while doing conservatory roof and the phone rings once, then go to the car write details, back on ladder and a phone rings again and have to go down, get it written down again.
Some times would not get a call for a whole day and some times 3 calls while doing one house.
Thinking that Lee has 10k -12k dropped in one day, I can't see a way of answering calls while working.
Lee well done !! Good luck with your campaign ! I am glad there are people who get so enthusiastic about running a business.