You cannot tell if a fence is yours just by looking at it.
It is possible that none of the fences surrounding your property belong to you.
The first step to deciding ownership should be to check your deeds and those of the adjoining landowner.
If you need advice have a look at this very informative website:- http://www.gardenlaw.co.uk/phpBB2/index.php
and btw, you havent said whether you mean front or back .. looking away from the house at the front is opposite to looking away from the house at the back. Not that it would make any difference anyway, as you cant tell unless you look at the deeds