I have a Tom Tom but frequently find that it won't accept postcodes, particularly if they are for service stations - three times lately it gives a strange location somewhere else in the world when you put in a postcode. Does anyone else get this problem or is it just my Sat Nav being a pillock as well as a total liar?
If it shows a location in another part of the world it means you have maps other than Europe and may have accidentally clicked on them. Go to settings, then maps and see if that is the case.