How Can You Prove That You Have Epilepsy?

I went away on a holiday this week but I forgot to take my medication with me, shit like this happens I forget things. I sat on the train going to London and I suddenly realised I had forgot my medication. I phoned my GP surgery as soon as I could and they said that I should temporarily register with another surgery which is the normal procedure. So I walked into the nearest surgery and I could not believe it when the receptionist said to me "I don't think we can help you very much unless you can prove you have epilepsy".

I mean how can you do that then? If I don't have any tablets for a while I could give you a ringside ticket when I do have a fit. I mean should I wear a t-shirt saying "I have epilepsy and I have been on the medication for almost 18 years". I did see a doctor eventually after waiting for over an hour and told him my predicament, gave him the number of my GP of which he phoned and he then gave me a prescription.

I have been thinking about having a t-shirt printed soon because my head injury is invisible and it affects me every day but it doesn't mean though that I am lazy or don't want to work. Any ideas?