Hi Glenn, I have had the same lying time wasters when I was looking for a 4 door Fiesta for my wife. Saw what looked like a nice red one, reasonable price, mileage etc. It was a fair distance from Southampton but after talking to the owner and asking straight out did it have any rust problems and being told "none at all, it is in really good condition" I went to view it.
When I got there the first thing I saw was that the way the photos had been taken showed the "good side" not the other side which looked like someone had painted it with a broom, was 3 different colours and had rust marks all over it! I did stay long enough to let the owner open it and there was a rust hole as big as your fist in the drivers door cill!! I was well pissed off asked the owner why she had lied to me about its condition. She didnt think there was anything wrong with it!!!
Luckily found the mrs a 1 elderly lady owner Renault Clio which was a time warp 2003 model with just 12500 miles from new with a full main dealer service history and it is still like a new car.
Wish you luck with your new Focus.