changing ip address

tell them you have been hacked and thus need dynamic.

That won't necessarily work as a PC avoidance strategy. They have many methods, from what I've heard.

any other angles?

You are an MI6 agent!

Just tell them that is what you want. Surely you dont need to give a reason!!

If they cant do it then jump ship.

My ISP(o2) charges to have a static address(if you want it).
However your IP address with O2 never changes anyway - unless you make it change. So anyone wanting static and paying is wasting their money.
Actually making it change is a bit fiddly.

Use this:

http://www.torproject.org/index.html.en