Car parked half on driveway half on pavement

I live in a student house and came back to find two of my housemates had parked on the drive (even though they have permits). One of them is away for the rest of the day I don't have a permit but my car is long so ive only managed to get half of it on the driveway. Could I be fined for this and do I have any defence? There's no where else to park