The starting level for BSAC instruction is Ocean Diver. You will learn the basics of open water diving, how to use the equipment and how to safely dive with a buddy. It has a combination of theory lessons, pool training sessions and open water dives to confirm your skills. This is done at your pace, no set time scale but can be completed within 2 months. the course does include basic use of enriched air and dry suit if required (extra hire cost). Most kit up to the open water stage can be loaned from the club.
More info can be found at https://www.bsac.com/training/learn-to-scuba-dive/ocean-diver-course/#tab-2
The initial membership is for 12 months and includes post qualification training, pool sessions, further qualifications if you want to progress your knowledge and experience at minimal costs.
Additional costs other than club membership and learning materials are entrance to dive sites, travel costs and open water kit hire if required, i.e. dry suit.