I have just purchased 2 badges.
I am based in the UK and we are coming over for a holiday and inc GenCon2016 in this.
As we can not select the UPs delivery option we are collecting via Will Call. It states you need government issued ID to collect.
Can I presume UK passort is fine for this?
Yes. From the Gen Con site:
UK passport has worked just fine for us the last... more years than I care to remember, actually ;)