I'm currently in my 4th year of the MEng Electronic Engineering with Music Technology Systems program at York. I also do guiding at interview days sometimes, so i know a bit about this.
Don't worry about the interview. Don't worry at all. I had mine a long time ago (5 years... wow), and yes they did ask me a maths question, which was kinda hard. BUT really it's the way you think which they are interested in. The interviewers will help you out if you get stuck, giving you hints, and as long as you manage to show that you can think then it will be fine.
Also, keep in your mind that the department probably wants you more than you want it (at this stage...). York is a fantastic place, but EE in general is undersubscribed. Just show interest in the subject and be chatty if you can. All the lecturers that interview (and in general actually) are really nice.
And just in case you're still worried, remember that the interview is your opportunity to impress. During my interview the academic asked if i thought i'd get the required grades, AAB, i said "probably not, I'm looking at ABB". The offer that i got was the ABB i asked for. And then... when i missed this by a grade i was *still* accepted, because i had impressed at interview.
But yeh, just remember that they want you and will be giving you the opportunity to impress them.
Hope you enjoy it.