The site offers 3 options of premium memberships:
For six months membership you need to pay 29.70 USD (4.95USD per month),
For three months membership you need to pay 23.85 USD (7.95 USD per month),
For one month membership you need to pay 9.95 USD.
So, it is apparent that the best option on the Britslr site is the longest membership with the cheapest rate.