There are no formal entry requirements, so it shouldn't matter that you don't have GCSEs or A Levels. I would order a prospectus and have a look through it. As far as I'm aware, you should be able to use the credits to get into another university. The course takes 6 years, I think. Maybe check the UCL Institute of Archeology to see what they accept? If it doesn't say, maybe give them a call or send an email?