So last night my Mini was running fine and I was off to pick up a friend, got to his house and then when I pulled over and stopped the car started running really weak until it just suddenly cut out and wouldn't start again for at least 20-30 minutes and even when it did start again it was running hideously weak so I nursed it home and got a lift off another friend. Gone down to my car this morning and once again it's still running like a dog, look underneath and there's a relatively small puddle of oil slowly dripping off the sump.
Any ideas what might be causing these problems and how to fix them, I'm absolutely stuffed as I know absolutely nothing about engines, help!