From Skinny's retired terms page18. Technical requirements
Skinny Unlimited Broadband uses Carrier Grade NAT. This will not interfere with most uses of the internet.
oops - my bad.
I joined them in mid 2017 and the CG-NAT was already gone by then
My thanks to all the people who have taken the time to reply to my post.
I appreciate the time you have taken to do so and your thoughtful replies.
scuwp: Have you tried contacting 2 Degrees and seeing what deal that may be willing to offer if you re-sign for 12 months?
No I haven't to be honest.
It frightens me phoning their help desk in that in the past I have had to wait a long time before I can speak to someone.
From some of the replies I have had I might need to give it some more thought before I change providers.
Thanks to you and all the other posters for your replies.