24 is correct increasing to 28 next year
The Government plans to increase the annual leave entitlement from 4.8 weeks to 5.6 weeks from 1 April 2009. If you work a five-day week, your holiday entitlement will increase from 24 days to 28 days (pro rata for part-time staff). If you already get 5.6 weeks' leave, your leave entitlement will not change
copied from acas website