Apologies for delayed response, I have been doing some digging (relationships, PKs) in the light of Bilbo's response - thank you for the input Bilbo.
Following concluded:
What I have so far does in fact work, the problem is with the (my) query and form/subform setups.
The organisations are...
I was going to say before I screw it up, but that would have made the title too long.
I've read some forum history and done some searches and can't see that a similar query has come up previously - but if anyone can point me at previous relevant threads then that would be much appreciated. I've...