Guust

GD takes its cities and towns from the Google API, and as far as I know is not based on postcode, but on city name. So if Google thinks the business is located in a suburb (or whatever you call outlying areas in the UK) with a different name than Bristol, you will need the GD Multilocations addon: https://wpgeodirectory.com/addons/multilocation/
That will allow you to add businesses with a different city address than Bristol.
Can you post the exact address you want to add and your URL, then we can have a better look, you can do that in a private message if you like.

All listings pages use the same template, so you cannot change the view per CPT without custom coding.

You can add widgets to the listings pages by adding them to the bottom section (and the sidebar(s) of course).
And you can move the bottom section next to the sidebar by manipulating the listings template a bit.
http://docs.wpgeodirectory.com/customizing-geodirectory-templates/

Why not ask people to sign up when registering?
You are in danger of being marked a spammer if you start sending regular emails without your users opting in.
https://wordpress.org/plugins/mailchimp-for-wp/

That is not possible for the moment.

Services as CPT, categories are beauty, health, business, legal, etc
You can use subcategories too.
http://docs.wpgeodirectory.com/places-categories-and-listings/

Your call really, but better to keep broad categories rather than narrow in my opinion.

I deleted all locations that were in the duplicated country, and your location settings now seem fine. I guess this was a leftover of some earlier version when GD could not translate countries like it does now.

Let us know if there is anything wrong still.

I am guessing you are using GDF child theme, but a URL would be handy.
Try adding this to your child theme’s CSS:

.geodir-content-right {padding-top: 10px;}

Here is a handy reference to do CSS tweaks yourself:
http://docs.wpgeodirectory.com/customizing-your-style/