Back in about 2006/07 I purchased an IPB licence (I think it was during version 2). I've since forgotten the email and password I used to log in and am wondering how I'd go about getting it?

I'd suggest directly emailing accounts@invisionpower.com with as many details of the purchase as you have or can remember. Customer Service should be able to locate the purchase if it was a Standard License.

Thank you @Mark H.