Hi Chris, in answer to your questions:
1. Yes you can set the expiry date for ads in the ClassiPress admin dashboard, whether it's a general expiry for all listings, or specific to an ad pack purchased. When the ad expires, is goes back to draft mode and is no longer visible on the site.
2. Yes, you can moderate ads before they are published for free ads, but paid ads do publish automatically.
3. Yes, you can simply update the field values and rename the default "State" field and update with the UK locations. This section to update can be seen from the
ClassiPress admin demo.
Thanks :)