We had bought an old house in France. Although it was basically sound - indeed, even habitable (almost) - it did need a bit of tarting up. Like completely redecorating.
We had decided on the simple approach - woodchip wallpaper and emulsion paint throughout. I had very carefully measured the rooms and, sitting in one of my favourite local restaurants with an old envelope, I did some calculations and worked out that I would need a hundred and seventeen rolls of wallpaper. That didn't seem quite right so I abandoned arithmetic in favour of bavette à l'echalotte and chips, washed down with a very passable local red wine. I even had a second cup of coffee.
I tried measuring the walls again after breakfast the next day and found that if I used feet instead of centimetres (or maybe it was the other way round) the answer was quite different, but I was still going to need fifty-three rolls of paper. The cashier at B & Q nearly had apoplexy when she saw me approach with not just one or even two but three trolleys, each one loaded to the brim with woodchip wallpaper. I had completely cleared their shelf and was still six rolls short. I was given some rather odd looks as I went through the security check before boarding the ferry at Portsmouth when the car seemed to contain nothing but me and woodchip wallpaper.