Type

"David LLoyd"+membership+cancel

into Google, for details of experiences of others. One entry leads to

http://www.oft.gov.uk/advice_and_res...traders/249/1/

Which indicates that David Llloyd were required to reduce minimum
membership/cancellation period from 6 months to 3 months, presumably
because six months was a unfair term. That may mean a minimum of three
months, if you've actually contracted to join, may have been deemed
'fair'. I'd still suggest confirming this, and your actual contractual
situation, with Citizen's Advice.

Toom