£2.35 a session, so works out at about £30 a month. I am restricted in my hours though,I have to go in between 9-4 on weekdays and 10-12 on weekends or I have to pay double (students get in half price during these times). e.g. if I go in at 3.50 pm, I get in for £2.35, but if I go in at 4pm it costs me £4.70.
Considering going for the full membership, which will allow me to go whenever I want, as often as I want for just over £30 a month.