Clearing pre-regestering problem

I applied to Swansea this ucas cycle and after hours of research and deep thoughts, i decided to reject Swansea in favour of Aberystwyth as my insurance, thing is that Swansea sent me an email today about registering "my interest" for clearing at Swansea just incase i dont make it into Aber. It asks for my Ucas application scheme code but i dont know what that is or where i can find it. I put in UC01 or UCAS01 but it doesnt work.
Any help to where i can find my code? Thanks.
They did actually lower the grades required for my offer and i think the admission tutor liked me but one of the big things (which is in the back of my head) is that incase i get maybe one or 2 grades lower than the offer i would be left in clearing with no university and no accommodation whereas i felt Aber would accept me.. that , i think, made the final decision for my insurance. Swansea have emailed me saying if i change my mind (alot but im pretty sure its a template email) let them know.
Any help please?