I've just signed up for a business account to manage a few accounts, but I'm not given the option to use paypal as payment.

My account that I signed up to business with is a new account, but one of the other admin accounts has been around for a while and has positive history. Neither one of the accounts can choose paypal.

Can anyone shed any light on it?

Not all Payment methods are present in all locations and countries. Not knowing what country you are doing this in, it is hard to guess. Addtionally, you cannot use the same PayPal account for the Skype control panel as another account maybe using as well.

We're in New Zealand, but have also tried from a server in the US (to see if it was limiting due to IP). Have changed country from New Zealand to US as well, but it still doesn't show up.

It doesn't even give me the option to choose paypal, let alone enter a paypal address.

Has the Skype Name you are using ever used PayPal as a Payment Method?

One of the accounts that administers the business account has got a paypal account attached to it. The other one I haven't bothered yet.