Eurail passes aren't valid in Great Britain (England, Scotland and Wales). However, your pass does entitle you to discounts on travel to London with the Eurostar train or to 1 location in England by ferry.
If you choose a Eurail Select Pass valid in both Greece and Italy, the ferry crossing between these countries is included in your pass, operated by Superfast Ferries,Blue Star Ferries and Minoan Lines (you just pay seasonal surcharges, port taxes and fuel surcharges).
In the Eurail Select Pass, Spain is bordered by Portugal and Italy. France is not part of the Select Pass and is therefore not a bordering country. Here’s how you can travel to Spain and Portugal (you must travel through Spain to reach Portugal) with a Eurail Select Pass:
From Italy you can take a discounted ferry to Spain.
From Paris you can take the Elipsos night train to Madrid or Barcelona (you must buy point-to-point tickets to travel within France).
Ireland is classed as a bordering country to the Benelux (Belgium, Netherlands and Luxembourg). France previously bordered with Ireland but no longer participates in the Eurail Select Pass. Your Eurail Select Pass entitles you to travel by discounted ferry between Ireland and France.