I ordered a 30% discount voucher from the National Express West Midlands website, so that I could go to Thinktank without paying full price. The online discount on the Thinktank website was only 10%, so was better having the one from the bus. Shortly after taking this, I went up to the new ticket booth / office (outside the new Science Garden / Kids Garden), presented the print out of my e-mail, and only had to pay £8.57.