Thank you for your responses and advice, most helpful! I am not alone...
I found an independent web page which includes a number of LinkedIn email addresses, so I will try one of those and CC the rest, with a threat of a complaint to the information commissioner and see how that goes...
https://support.linkedhelper.com/hc/...pport-directly
https://ico.org.uk/make-a-complaint/...on-complaints/
Cheers, Treadders