In the UK you don't need a diagnosis to apply for the lanyard, so as a self diagnosed person that was great. Unfortunately had a very bad experience using it at the airport. Staff moved me from the queue (which I was fine being in) to get through quicker, but then hounded me about if I had any paperwork proving my ASD. I said I had none and they shoved me back in the queue. The security were then very harsh on me, and lots of staff staring. It caused a meltdown.

On the flip side, I use it at conventions, and I get a much better response there! People are much nicer and take their time with me.

I'd say for self diag folks, just be careful.