I paid 15 GBP admission fee and asked at cashier if i can go in and out whenever I want.
They told me yes with big smile and i got stamp on my hand.
After spending 1 hour there i went out for 30 min and then i came back, The bouncer(same one that got me in) said: "you cant come in its another venue started inside and you have to queue in line and pay one more admission fee".