Thanks for your reply Marco. 

Thinking of private sellers especially who will just take an address on face value, write it out on their parcel and put a stamp on, it is asking for a lost or delayed parcel. With my buyer, I still can't fathom what they have done as the Manchester part of the address doesn't seem to exist as a street anyway and they still aren't replying.

It would be good if eBay could automatically recognise an address as invalid when they add it to their profile, it will reduce the number of cancelled or refunded sales which is beneficial for eBay as well as users. Thanks