I marked my 60th by organising lunch in a private room of a central London pub for family and friends. There were around 30 of us; the cost was surprisingly reasonable and, because it was central London, it was easily accessible by train from all parts of the country so lots of "long distance" friends were able to be there.
This year will be my 70th and I may well do something similar .
Some years ago, I encountered a group of very giggly French women on a Dover/Calais ferry. One of them was celebrating her 75th birthday and they'd hired a minibus with driver and treated themselves to a weekend in England, doing the tourist sights in Kent; a couple of nights in London with shopping, tourist trail, etc. They were on the homeward run when I met them and clearly having lots of fun in the ship's bar. Maybe Sb and friends might enjoy the reverse - a weekend in Paris (if the strikes ever end) or perhaps Brussels or Amsterdam?