Sorry that I'm a bit late replying to this.
"Yes absolutely right about leading questions. I think I need to come up with some that weave them through their life experience."
A good way I found of coming up with leading questions was to find out what I could about family members from the likes of Ancestry and then ask my parents about those things (for context, my parents are in their 80s).
A couple of examples, I came across records on Ancestry that suggested that my mum's older cousin got pregnant at 15, very quickly married to a US airman, lied about her age and was then one of the first US war brides to be transported to America after the war.
I then just popped into the conversation with my mum one time "Oh, do you remember having a cousin Xxxx at all? Did she get married?"
That brought it all back and she began telling me her recollections of her cousin and what had happened (that was largely consistent with the records I had already seen) and other family stories. My mum was only six when her cousin got married but she remembered the cousin's fiance (the US airman) and another coming to visit one time and taking the time to play with her - she was very impressed by their uniforms.
All of that was sparked by just knowing there was a story there and mentioning a name.
Another example, I found out that my dad's maternal grandfather fought in World War One right from the start in August 1914 in France and then Salonika until 1919. For some reason, he didn't get his campaign medals until 1939.
So, I asked my dad if he ever remembered anything about his grandfather and had he been in the army. Again, this got my dad talking and remembering things about his grandfather and also stories that he had heard about his grandfather when he (my dad) was young.
Leading questions (especially when you know that there is a story there) really can help a lot.