Alton Towers,Can't book on-line

I have been trying to book tickets and accomodation on the Alton Towers website but it will not let me because it insists on a Postal Code being entered.
I've tried puting in NA or leaving it blank,no go,anyone any ideas?
Tried ringing them but booking is closed for now.

P.S Anyone been there?,its our first time.

Try typing in EIRE and see if it will take it, it has worked for me on a few ocassions.