Post Codes formatting errors
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.

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Nicky commented
Please add postcode space checker for integrated orders.
The post codes are entered within Etsy by the customer and some of them don't add a space SK115LZ instead of SK11 5LZ. The orders are then integrated with this mistake.
These customer orders are delayed within the RM system and I invariably have to refund their order due to late delivery. Then I have to refund my order with the Royal Mail software.The space checker could flag this or ideally see the error and add a space