Replacing like-for-like would be simple solution however the manufacturers are trying so hard to engineer obsolescent products that the chances of having four the same are virtually nil.
To cut a long story short, I now have a suitably at'tire'd car with 4 strips of rubber round the circular metal things and a certificate of road worthiness that is technically worthless assuming the man remembers to punch the right keys on the VOSA Database. Huzzah!