So we decided with all these thread flying around about the pitfalls of switching ISPs, that we would write a blog article about it - might be handy to refer back to in the future as it seems remarkably common.
http://pages.bigpipe.co.nz/how-to-switch-isps-without-ruining-everything/
If you guys have any other tips to add we'd love to hear them and we can incorporate them into the article.
It also contains this cartoon for a handy reference