@Andy Selwood - Welcome to the forum. Your location in your profile adds context to your posts and helps others give better answers to questions, provide more useful resources, etc. Completely your choice on the level of accuracy.
We have a strong group of UK and EU riders on the forum that contribute often. They have many RTEs, (Rides To Eat), that you may find interesting, but do be aware that these are not group rides. Every rider simply makes their way to the designated spot on their own. It can provide excellent opportunities to meet others and learn more about long distance riding. It is not uncommon for riders to pair up for the rides with prior communication.
Here is the IBA UK Sub forum -
Click ME I encourage you to post on the Introduction page there as well.
And the IBA Benelux
LINK which is a broader EU grouping.
Anyone is welcome, but the threshold for becoming an Iron Butt Association member, including the IBA UK, is the basic
SS1600Km ride. Successfully riding, documenting and submitting that will start off your IBA membership and give you a number that is referenced for other aspects of the IBA.
There are may resources here, on
ironbutt.org & the
Ironbutt UK site. Please enjoy poking around the sites and don't hesitate to ask questions!