Meanwhile, here in Bristol, a whole bunch of sites insist on using a drop down for the county and list "Avon" which doesn't even exist. It should be Bristol or possibly City of Bristol.

I think the county list is set in stone because Royal Mail refuses to update them (for some idiotic reason they still control the postcode database, which I guess lots of websites use and therefore use the old county names / boundaries). For example, it's still Humberside, even though that hasn't existed for decades.

Yep, I recall that Royal Mail is one of the websites that has the "Avon" issue. I don't know why they don't just update it to make it accurate as they update their PAF files for postcode lookups every three months with new postcodes. "Avon" is strange as it's still used in some contexts, such as the police force is known as Avon & Somerset