Thank you Visvanath
I read the forum discussion you linked - scary stuff, and it reminds me of the principle we used in a project (working with offenders) when deciding how to resolve a dilemma: 'how would this look on the front page of the local newspaper' There are no secrets online - I only have to see the endless adverts and emails with peripheral relevance to a search I've done, or a site I've visited to be reminded of that. As Sam Thing says in the forum "If I have no choice as to whether I have my privacy infringed or not, at least I should try and have some fun while it's happening."
In answer to your questions:
I have 2.5 on a hosted server, which has been suffering 'denial of service' attacks - putting it out of action for extended periods. My desire to have 2.5 on my laptop is because I have loads of development to do, and then I can upload new courses to the server. Of course, that would also mean I can work offline and that would be useful when out of wi-fi access. The laptop will never be 'live' to learners or any other sort of remote access.
In this forum, I have already had very helpful advice about the 'timeout' issue, which means we've been able to install a demo on one of the work laptops - I use this in presentations where there's no internet access.
I seem to have backed myself into an unresolvable error as a result of repeated attempts to instal Moodle on the laptop. If all else fails, I'll start again from scratch - altering the timeout settings before I start - and cross my fingers that it all goes more smoothly this time.