Are you worried about mobile phone masts in your area or just want to locate which mobile transmitter network is nearest to you?
If you put in your town or post code to the Ofcom website then you can see all the different mobile phone masts in your area and which mobile phone network company operates them.
http://www.sitefinder.ofcom.org.uk/search
There are many different designs of mobile phone masts now ranging from the traditional several elements arranged around a central pole to the more disguised designs that are more like thin lollipops!