I think you're misunderstanding what the static IP address is about.
The IP address is on your home network - not the "internet". The only device on your network that exists on the internet is actually your hub, and that can have a static address (unusual) or DHCP (much more common). This is completely independent of your Amiga.
Your Amiga can have a static IP address or DHCP (just about any TCP/IP stack apart from AmiTCP 3) will do DHCP without too much trouble, although there can be issues with some hubs, at which point you just use static IP. Whatever you do with your Amiga, though, it only makes a difference between your Amiga and your hub - the connection between your hub and the rest of the world stays the same.
In other words - don't worry about it.
The only way it would be a problem is if your hub were to not support static IP on its internal (your home) network, which would be incredibly brain-dead. That said, of course, Sky are pretty brain-dead... but I think you'll be ok.
