Thanks for your reply, Nic.
I purchased a new subscription with Jomsocial today and I would like to explain the situation.
At the moment we have a Joomla 3.5 site, running on PHP 5.6.4, using Jomsocial 4.1.6.
We are looking to update at least to Joomla 3.10 and I would have to know the best update path for that.
Thanks for any ideas, inputs or links to the referring documentation.