How do i find a snake?

i live in England and I realy want to see a snake in the wild because i have never seen one before and i am very passionate about them. I won't harm one or catch one i just want to see one and maybe take a picture of it. The snakes we get in England are the grass snake (which i think is like the garter snake), the adder (which is our only venomous snake) and finally the smooth snake which is the rarest to find apparently. I have tried to see one beforeby place a tin out in an open field with long grass in next to a woodland. I check it regulary but there is never anything there. It is right next to a lake as well and i heard that there favourite food lives there (the frog). No horrible answers. Plzz help! What am i doing wrong?