Cheaper phone calls.

If you ever have to ring one of the 0870, 0845 type numbers. Go to this website, select the 'Search to find an alternative number.' on the bottom left of the top banner, :?  :shock:  and put the company name or number in and invariably it will give a cheaper, landline alternative:- http://www.saynoto0870.com/

It's great, I don't know if whoever answers the phones can tell that you've called the free/cheaper number, but they always sounds slightly mardy!!  

I don't know if whoever answers the phones can tell that you've called the free/cheaper number

No, the geographical number is their real number. In these days of computerised communication an 0870x or 0845x is translated to the geographical number by the computer (digital exchange).

The exception is that I use a Swiss company for my calls during the week, and the person called has sometimes asked where I am calling from, as it apparently shows as an international number (although I am just up the road from them).