Please post code formatting errors, because post code entered like this: PP5 5XZ where double space is included generates errors.
So you will need to add filtering RegEx rules to handle this without generating errors. Also the lady on Royal Mail line 0345 2661 004 told me that the eBay customers often enters double city like London London which also generates some errors. I did not experienced any issues like this but address handling should be generally improved and as a developer I know this is easy and possible to achieve. Wondering why this is not done already.