Hi Piers and welcome to the Club.
I retired at 58 some 5 years ago and it was one of the two best things I have ever done.
It was my decision and I had decided that it was time to "look at all of the other rooms in my life"
I had occupied a senior position for the last 30 years and had sat in every chair,looked at every picture and fixed everything that needed fixing in that room.
I then saw a door I had not noticed once during my time in that room.I peeped inside and thought, wow!
I have often wondered during these past 15 years how on earth I had found the time to go to work.
Do whatever interests you.Be with whoever you wish to be with and importantly, read. Read anything and everything.Read from as many different perspectives as are available. Be available to those that seek your advice and give it freely.
I enjoy driving and drive to Spain twice yearly. I garden, play Golf, meet friends and watch Sports and filmsvia the Internet--it`s free, no need to pay silly and expensive subscriptions.
My Grandson has just introduced me to Harry Potter and I am trying to get him interested in Mercury, Gemini and Apollo !
It is worth remembering something along the lines of what the 35th President of the U.S.A. said......."ask not what your life can do for you, but ask what you can do for your life!
Once again, welcome to a whole new world of opportunity.