I am conducting research into the use of telephones in UK households.

I need to estimate the number of homes in each for the following
mutually exclusive categories:-

1.	Households that have a single telephone handset in use (either a
phone plugged into an extension socket or a single DECT (wireless)
phone
2.	How many have multiple telephone handsets plugged into multiple
extension sockets
3.	How many use a DECT (wireless) system with multiple handsets all
linked through from a single telephone socket.

As this is part of a research study I need you to cite an
authoritative referencable source for the information.