Hey,
I was in the smae position as you last night mate, you need to contact your bank ASAP, as this website isn't legit, or at least doesn't seem that way but would you like to take the chance. I spoke to festival republic today aswell and they have actually blacklisted the company, and for anyone who doesn't believe me, phone them for yourself.
Also, if you look at the website a little closer it becomes quickly apparent, it isnt one of a proper website. Last night it allowed me to purchase 999 tickets, which is kinda wierd considering the event is sold out. Once you select the tickets, you go onto the payment server, which isn't secure which again leads me question the legitmacy of the website. For that reason alone you should contact your bank. Finally, the website has a London telephone number but a registered address in Spain.
For all the above reasons, i decided that the website was fraudulent website, i was lucky i managed to contact the bank within an hour of the transaction which meant the money hadnt yet been authorised. But if, like me you agree that it doesnt seem right, and they've taken the money already, dont worry too much, most banks have some sort of insurance available.
But, please take note of my advice, do you really want to risk losing all that money? i certainly didnt. Oh yeah, after all this if your still want tickets, festival republic are releasing a second batch of tickets soon, so if like me you're gunning for one of them, GOOD LUCK.
Hope that helped and hope it all works out fine and if you have any more questions just ask, i'll be happy to answer them for you.