First let me say that if you were my child, I would ground you from unsupervised internet use for a very long time!
Second, you don't sound remorseful to me. You lied about your age, lying is bad. You admit you know that. The thing is, you don't even seem to comprehend, let alone be remorseful for, the danger you put everyone in the SL Adult Grid that came in contact with you in. It's as if you walked into a stripper bar and said, yeah but I only wanted to use the loo. Sorry, life doesn't work that way and at least in the US, laws don't work that way.
You have been provided with the solution to your problem many times here. It isn't going to change. Faxes are not common in the UK? How in the heck do they do business there then? Faxes are old school technology and I find it extremely difficult to believe that they are not used in the UK. So scan your passport and attach the file to the ticket, or the email.
It sounds to me as if you are trying to fix this before your parents find out. So not only did you lie and cause this mess, you are also not willing to "adult up" and take responsibility for your actions. You may as well deal with it now, because even though you teens think us old folks are dumb, we aren't!! In my household, if you pulled a stunt like this and did not own up to it, your punishment would increase for the double lie.
The solution is, tell your parents and have them assist you in sorting it all out. I'm sure they have access to a fax machine or know how to scan a document and attach it to an email. I think you are afraid they will punish you as I would which shows that you are not remorseful at all.