With no credit history in the UK, you might find things to be difficult.
When i first arrived, i did pay the 6 months in advance, because i had no job, no credit history, and at that stage, no leave to remain in the country! ... the landlord was happy, and i was happy, because i knew that no matter what else went wrong, at least i had a roof over my head for 6 months! (However, my rent was A LOT cheaper than what you are looking at!)